diff --git a/engine/core/animation/ActiveAnimations.h b/engine/core/animation/ActiveAnimations.h
index b5e946ddc44..5410762d59e 100644
--- a/engine/core/animation/ActiveAnimations.h
+++ b/engine/core/animation/ActiveAnimations.h
@@ -46,7 +46,7 @@ class Element;
 
 typedef HashCountedSet<RawPtr<AnimationPlayer> > AnimationPlayerCountedSet;
 
-class ActiveAnimations : public DummyBase<ActiveAnimations> {
+class ActiveAnimations {
     WTF_MAKE_NONCOPYABLE(ActiveAnimations);
 public:
     ActiveAnimations()
diff --git a/engine/core/animation/AnimationNode.h b/engine/core/animation/AnimationNode.h
index 8227ba598da..2b183ececf5 100644
--- a/engine/core/animation/AnimationNode.h
+++ b/engine/core/animation/AnimationNode.h
@@ -71,7 +71,7 @@ public:
         PhaseNone,
     };
 
-    class EventDelegate : public DummyBase<EventDelegate> {
+    class EventDelegate {
     public:
         virtual ~EventDelegate() { }
         virtual void onEventCondition(const AnimationNode*) = 0;
diff --git a/engine/core/animation/AnimationPlayer.h b/engine/core/animation/AnimationPlayer.h
index 02b25440aaa..beeee71f21a 100644
--- a/engine/core/animation/AnimationPlayer.h
+++ b/engine/core/animation/AnimationPlayer.h
@@ -46,7 +46,6 @@ class AnimationPlayer final : public RefCounted<AnimationPlayer>
     , public EventTargetWithInlineData {
     DEFINE_WRAPPERTYPEINFO();
     REFCOUNTED_EVENT_TARGET(AnimationPlayer);
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(AnimationPlayer);
 public:
     enum AnimationPlayState {
         Idle,
diff --git a/engine/core/animation/AnimationTimeline.h b/engine/core/animation/AnimationTimeline.h
index bd1cdb67413..01dbe071a93 100644
--- a/engine/core/animation/AnimationTimeline.h
+++ b/engine/core/animation/AnimationTimeline.h
@@ -50,7 +50,7 @@ class AnimationNode;
 class AnimationTimeline : public RefCounted<AnimationTimeline>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    class PlatformTiming : public DummyBase<PlatformTiming> {
+    class PlatformTiming {
 
     public:
         // Calls AnimationTimeline's wake() method after duration seconds.
diff --git a/engine/core/animation/InterpolableValue.h b/engine/core/animation/InterpolableValue.h
index a3a55fb6a73..3f975508864 100644
--- a/engine/core/animation/InterpolableValue.h
+++ b/engine/core/animation/InterpolableValue.h
@@ -12,7 +12,7 @@
 
 namespace blink {
 
-class InterpolableValue : public DummyBase<InterpolableValue> {
+class InterpolableValue {
     DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(InterpolableValue);
 public:
     virtual bool isNumber() const { return false; }
diff --git a/engine/core/animation/InterpolationEffect.h b/engine/core/animation/InterpolationEffect.h
index c7436e02973..cd8631e2b11 100644
--- a/engine/core/animation/InterpolationEffect.h
+++ b/engine/core/animation/InterpolationEffect.h
@@ -30,7 +30,7 @@ private:
     {
     }
 
-    class InterpolationRecord : public DummyBase<InterpolationRecord> {
+    class InterpolationRecord {
     public:
         RefPtr<Interpolation> m_interpolation;
         RefPtr<TimingFunction> m_easing;
diff --git a/engine/core/animation/Keyframe.h b/engine/core/animation/Keyframe.h
index 414972a4c89..38ee1c4e584 100644
--- a/engine/core/animation/Keyframe.h
+++ b/engine/core/animation/Keyframe.h
@@ -50,7 +50,7 @@ public:
 
     virtual void trace(Visitor*) { }
 
-    class PropertySpecificKeyframe : public DummyBase<PropertySpecificKeyframe> {
+    class PropertySpecificKeyframe {
     public:
         virtual ~PropertySpecificKeyframe() { }
         double offset() const { return m_offset; }
diff --git a/engine/core/animation/KeyframeEffectModel.h b/engine/core/animation/KeyframeEffectModel.h
index 50f00608361..3a856fc7868 100644
--- a/engine/core/animation/KeyframeEffectModel.h
+++ b/engine/core/animation/KeyframeEffectModel.h
@@ -55,7 +55,7 @@ public:
     // FIXME: Implement accumulation.
 
     typedef Vector<OwnPtr<Keyframe::PropertySpecificKeyframe> > PropertySpecificKeyframeVector;
-    class PropertySpecificKeyframeGroup : public DummyBase<PropertySpecificKeyframeGroup> {
+    class PropertySpecificKeyframeGroup {
     public:
         void appendKeyframe(PassOwnPtr<Keyframe::PropertySpecificKeyframe>);
         const PropertySpecificKeyframeVector& keyframes() const { return m_keyframes; }
diff --git a/engine/core/animation/SampledEffect.h b/engine/core/animation/SampledEffect.h
index 222e420a040..28348521a77 100644
--- a/engine/core/animation/SampledEffect.h
+++ b/engine/core/animation/SampledEffect.h
@@ -13,7 +13,7 @@
 
 namespace blink {
 
-class SampledEffect : public DummyBase<SampledEffect> {
+class SampledEffect {
 public:
     static PassOwnPtr<SampledEffect> create(Animation* animation, PassOwnPtr<Vector<RefPtr<Interpolation> > > interpolations)
     {
diff --git a/engine/core/animation/css/CSSAnimations.h b/engine/core/animation/css/CSSAnimations.h
index ae2da9120d3..a46659dd526 100644
--- a/engine/core/animation/css/CSSAnimations.h
+++ b/engine/core/animation/css/CSSAnimations.h
@@ -52,7 +52,7 @@ class StyleRuleKeyframes;
 
 // This class stores the CSS Animations/Transitions information we use during a style recalc.
 // This includes updates to animations/transitions as well as the Interpolations to be applied.
-class CSSAnimationUpdate final : public DummyBase<CSSAnimationUpdate> {
+class CSSAnimationUpdate final {
 public:
     void startAnimation(AtomicString& animationName, PassRefPtr<InertAnimation> animation)
     {
diff --git a/engine/core/animation/css/CSSTimingData.h b/engine/core/animation/css/CSSTimingData.h
index 182ea69d382..00d890cd7af 100644
--- a/engine/core/animation/css/CSSTimingData.h
+++ b/engine/core/animation/css/CSSTimingData.h
@@ -13,7 +13,7 @@ namespace blink {
 
 struct Timing;
 
-class CSSTimingData : public DummyBase<CSSTimingData> {
+class CSSTimingData {
 public:
     ~CSSTimingData() { }
 
diff --git a/engine/core/css/CSSCalculationValue.cpp b/engine/core/css/CSSCalculationValue.cpp
index 60b9eb40756..144de04001e 100644
--- a/engine/core/css/CSSCalculationValue.cpp
+++ b/engine/core/css/CSSCalculationValue.cpp
@@ -182,7 +182,7 @@ double CSSCalcValue::computeLengthPx(const CSSToLengthConversionData& conversion
 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CSSCalcExpressionNode)
 
 class CSSCalcPrimitiveValue final : public CSSCalcExpressionNode {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
 
     static PassRefPtr<CSSCalcPrimitiveValue> create(PassRefPtr<CSSPrimitiveValue> value, bool isInteger)
diff --git a/engine/core/css/CSSCanvasValue.h b/engine/core/css/CSSCanvasValue.h
index c2c16a00e78..ca8ad606ee4 100644
--- a/engine/core/css/CSSCanvasValue.h
+++ b/engine/core/css/CSSCanvasValue.h
@@ -63,8 +63,7 @@ private:
 
     // NOTE: We put the CanvasObserver in a member instead of inheriting from it
     // to avoid adding a vptr to CSSCanvasValue.
-    class CanvasObserverProxy final : public DummyBase<CanvasObserverProxy>, public CanvasObserver {
-        WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(CanvasObserverProxy);
+    class CanvasObserverProxy final : public CanvasObserver {
     public:
         explicit CanvasObserverProxy(CSSCanvasValue* ownerValue) : m_ownerValue(ownerValue) { }
 
diff --git a/engine/core/css/CSSDefaultStyleSheets.cpp b/engine/core/css/CSSDefaultStyleSheets.cpp
index 518b1f1c2cc..7471b99054f 100644
--- a/engine/core/css/CSSDefaultStyleSheets.cpp
+++ b/engine/core/css/CSSDefaultStyleSheets.cpp
@@ -83,16 +83,4 @@ CSSDefaultStyleSheets::CSSDefaultStyleSheets()
     m_defaultViewportStyle->addRulesFromSheet(viewportStyleSheet(), screenEval());
 }
 
-void CSSDefaultStyleSheets::ensureDefaultStyleSheetsForElement(Element* element, bool& changedDefaultStyle)
-{
-}
-
-void CSSDefaultStyleSheets::trace(Visitor* visitor)
-{
-    visitor->trace(m_defaultStyle);
-    visitor->trace(m_defaultViewportStyle);
-    visitor->trace(m_defaultStyleSheet);
-    visitor->trace(m_viewportStyleSheet);
-}
-
 } // namespace blink
diff --git a/engine/core/css/CSSDefaultStyleSheets.h b/engine/core/css/CSSDefaultStyleSheets.h
index aafedbf7eef..50fd869037c 100644
--- a/engine/core/css/CSSDefaultStyleSheets.h
+++ b/engine/core/css/CSSDefaultStyleSheets.h
@@ -23,7 +23,8 @@
 #ifndef CSSDefaultStyleSheets_h
 #define CSSDefaultStyleSheets_h
 
-#include "platform/heap/Handle.h"
+#include "wtf/OwnPtr.h"
+#include "wtf/RefPtr.h"
 
 namespace blink {
 
@@ -31,20 +32,16 @@ class Element;
 class RuleSet;
 class StyleSheetContents;
 
-class CSSDefaultStyleSheets : public DummyBase<CSSDefaultStyleSheets> {
+class CSSDefaultStyleSheets {
 public:
     static CSSDefaultStyleSheets& instance();
 
-    void ensureDefaultStyleSheetsForElement(Element*, bool& changedDefaultStyle);
-
     RuleSet* defaultStyle() { return m_defaultStyle.get(); }
     RuleSet* defaultViewportStyle() { return m_defaultViewportStyle.get(); }
 
     StyleSheetContents* defaultStyleSheet() { return m_defaultStyleSheet.get(); }
     StyleSheetContents* viewportStyleSheet() { return m_viewportStyleSheet.get(); }
 
-    void trace(Visitor*);
-
 private:
     CSSDefaultStyleSheets();
 
diff --git a/engine/core/css/CSSFontFace.h b/engine/core/css/CSSFontFace.h
index 159c519f6dc..4284ffa3ae5 100644
--- a/engine/core/css/CSSFontFace.h
+++ b/engine/core/css/CSSFontFace.h
@@ -43,7 +43,7 @@ class RemoteFontFaceSource;
 class SimpleFontData;
 class StyleRuleFontFace;
 
-class CSSFontFace final : public DummyBase<CSSFontFace> {
+class CSSFontFace final {
 public:
     struct UnicodeRange;
     class UnicodeRangeSet;
diff --git a/engine/core/css/CSSFontFaceSource.h b/engine/core/css/CSSFontFaceSource.h
index 5c6f72d7e58..943fcd67d2b 100644
--- a/engine/core/css/CSSFontFaceSource.h
+++ b/engine/core/css/CSSFontFaceSource.h
@@ -36,7 +36,7 @@ class CSSFontFace;
 class FontDescription;
 class SimpleFontData;
 
-class CSSFontFaceSource : public DummyBase<CSSFontFaceSource> {
+class CSSFontFaceSource {
 public:
     virtual ~CSSFontFaceSource();
 
diff --git a/engine/core/css/CSSFontSelectorClient.h b/engine/core/css/CSSFontSelectorClient.h
index 08e85ecc037..ebb0d88c028 100644
--- a/engine/core/css/CSSFontSelectorClient.h
+++ b/engine/core/css/CSSFontSelectorClient.h
@@ -38,7 +38,7 @@ namespace blink {
 class CSSFontSelector;
 class Visitor;
 
-class CSSFontSelectorClient : public DummyBase<CSSFontSelectorClient> {
+class CSSFontSelectorClient {
 public:
     virtual ~CSSFontSelectorClient() { }
 
diff --git a/engine/core/css/CSSKeyframeRule.h b/engine/core/css/CSSKeyframeRule.h
index 1a386e85efd..46714c85979 100644
--- a/engine/core/css/CSSKeyframeRule.h
+++ b/engine/core/css/CSSKeyframeRule.h
@@ -38,7 +38,7 @@ class StylePropertySet;
 class StyleRuleCSSStyleDeclaration;
 
 class StyleKeyframe final : public RefCounted<StyleKeyframe> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<StyleKeyframe> create()
     {
diff --git a/engine/core/css/CSSRuleList.h b/engine/core/css/CSSRuleList.h
index 4a7b5bf9f15..e5da780f6f1 100644
--- a/engine/core/css/CSSRuleList.h
+++ b/engine/core/css/CSSRuleList.h
@@ -23,7 +23,7 @@
 #define CSSRuleList_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
-#include "platform/heap/Handle.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
@@ -33,9 +33,9 @@ namespace blink {
 class CSSRule;
 class CSSStyleSheet;
 
-class CSSRuleList : public DummyBase<CSSRuleList>, public ScriptWrappable {
+class CSSRuleList : public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
     WTF_MAKE_NONCOPYABLE(CSSRuleList);
 public:
     virtual ~CSSRuleList();
diff --git a/engine/core/css/CSSStyleDeclaration.h b/engine/core/css/CSSStyleDeclaration.h
index 961fcad53c7..4d51e5ad039 100644
--- a/engine/core/css/CSSStyleDeclaration.h
+++ b/engine/core/css/CSSStyleDeclaration.h
@@ -35,9 +35,9 @@ class CSSValue;
 class ExceptionState;
 class MutableStylePropertySet;
 
-class CSSStyleDeclaration : public DummyBase<CSSStyleDeclaration>, public ScriptWrappable {
+class CSSStyleDeclaration : public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
-    WTF_MAKE_NONCOPYABLE(CSSStyleDeclaration); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_NONCOPYABLE(CSSStyleDeclaration); WTF_MAKE_FAST_ALLOCATED;
 public:
     virtual ~CSSStyleDeclaration() { }
 
diff --git a/engine/core/css/CSSValuePool.h b/engine/core/css/CSSValuePool.h
index 7e9721bd0db..84eca8dc4cd 100644
--- a/engine/core/css/CSSValuePool.h
+++ b/engine/core/css/CSSValuePool.h
@@ -39,8 +39,8 @@ namespace blink {
 
 class CSSValueList;
 
-class CSSValuePool :  public DummyBase<CSSValuePool> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class CSSValuePool {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     PassRefPtr<CSSValueList> createFontFaceValue(const AtomicString&);
     PassRefPtr<CSSPrimitiveValue> createFontFamilyValue(const String&);
diff --git a/engine/core/css/FontFaceSetForEachCallback.h b/engine/core/css/FontFaceSetForEachCallback.h
index 15c70c78582..b7b6c1ce8a1 100644
--- a/engine/core/css/FontFaceSetForEachCallback.h
+++ b/engine/core/css/FontFaceSetForEachCallback.h
@@ -34,7 +34,7 @@ namespace blink {
 class FontFace;
 class FontFaceSet;
 
-class FontFaceSetForEachCallback : public DummyBase<FontFaceSetForEachCallback> {
+class FontFaceSetForEachCallback {
 public:
     virtual ~FontFaceSetForEachCallback() { }
     virtual void trace(Visitor*) { }
diff --git a/engine/core/css/MediaQuery.h b/engine/core/css/MediaQuery.h
index 6ce4683bbb4..6b43a329ec6 100644
--- a/engine/core/css/MediaQuery.h
+++ b/engine/core/css/MediaQuery.h
@@ -40,8 +40,8 @@ class MediaQueryExp;
 
 typedef Vector<OwnPtr<MediaQueryExp> > ExpressionHeapVector;
 
-class MediaQuery : public DummyBase<MediaQuery> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class MediaQuery {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     enum Restrictor {
         Only, Not, None
diff --git a/engine/core/css/MediaQueryExp.h b/engine/core/css/MediaQueryExp.h
index 4968cb5427a..68d1bb48a07 100644
--- a/engine/core/css/MediaQueryExp.h
+++ b/engine/core/css/MediaQueryExp.h
@@ -76,8 +76,8 @@ struct MediaQueryExpValue {
     }
 };
 
-class MediaQueryExp  : public DummyBase<MediaQueryExp> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class MediaQueryExp  {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<MediaQueryExp> createIfValid(const String& mediaFeature, CSSParserValueList*);
     ~MediaQueryExp();
diff --git a/engine/core/css/MediaQueryList.h b/engine/core/css/MediaQueryList.h
index a445401cd86..75329bce43e 100644
--- a/engine/core/css/MediaQueryList.h
+++ b/engine/core/css/MediaQueryList.h
@@ -47,7 +47,6 @@ class MediaQuerySet;
 class MediaQueryList final : public RefCounted<MediaQueryList>, public EventTargetWithInlineData, public ActiveDOMObject {
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCounted<MediaQueryList>);
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(MediaQueryList);
 public:
     static PassRefPtr<MediaQueryList> create(ExecutionContext*, PassRefPtr<MediaQueryMatcher>, PassRefPtr<MediaQuerySet>);
     virtual ~MediaQueryList();
diff --git a/engine/core/css/RuleSet.h b/engine/core/css/RuleSet.h
index f23bbfe7192..0139011c85d 100644
--- a/engine/core/css/RuleSet.h
+++ b/engine/core/css/RuleSet.h
@@ -77,9 +77,9 @@ struct SameSizeAsRuleData {
 
 COMPILE_ASSERT(sizeof(RuleData) == sizeof(SameSizeAsRuleData), RuleData_should_stay_small);
 
-class RuleSet : public DummyBase<RuleSet> {
+class RuleSet {
     WTF_MAKE_NONCOPYABLE(RuleSet);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<RuleSet> create() { return adoptPtr(new RuleSet); }
 
@@ -132,7 +132,7 @@ private:
     void compactRules();
     static void compactPendingRules(PendingRuleMap&, CompactRuleMap&);
 
-    class PendingRuleMaps : public DummyBase<PendingRuleMaps> {
+    class PendingRuleMaps {
     public:
         static PassOwnPtr<PendingRuleMaps> create() { return adoptPtr(new PendingRuleMaps); }
 
diff --git a/engine/core/css/StyleRule.h b/engine/core/css/StyleRule.h
index 6ab9061103b..eb992b5b749 100644
--- a/engine/core/css/StyleRule.h
+++ b/engine/core/css/StyleRule.h
@@ -36,7 +36,7 @@ class MutableStylePropertySet;
 class StylePropertySet;
 
 class StyleRuleBase : public RefCounted<StyleRuleBase> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     enum Type {
         Unknown, // Not used.
@@ -91,7 +91,7 @@ private:
 };
 
 class StyleRule : public StyleRuleBase {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<StyleRule> create() { return adoptRef(new StyleRule()); }
 
diff --git a/engine/core/css/invalidation/StyleInvalidator.h b/engine/core/css/invalidation/StyleInvalidator.h
index 6fb4e624329..281bc39334f 100644
--- a/engine/core/css/invalidation/StyleInvalidator.h
+++ b/engine/core/css/invalidation/StyleInvalidator.h
@@ -6,6 +6,8 @@
 #define StyleInvalidator_h
 
 #include "platform/heap/Handle.h"
+#include "wtf/HashMap.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
diff --git a/engine/core/css/resolver/MatchedPropertiesCache.h b/engine/core/css/resolver/MatchedPropertiesCache.h
index d91a77e256f..d5913628f8d 100644
--- a/engine/core/css/resolver/MatchedPropertiesCache.h
+++ b/engine/core/css/resolver/MatchedPropertiesCache.h
@@ -36,7 +36,7 @@ namespace blink {
 class RenderStyle;
 class StyleResolverState;
 
-class CachedMatchedProperties final : public DummyBase<CachedMatchedProperties> {
+class CachedMatchedProperties final {
 
 public:
     Vector<MatchedProperties> matchedProperties;
diff --git a/engine/core/css/resolver/MediaQueryResult.h b/engine/core/css/resolver/MediaQueryResult.h
index 8b6a2051096..a1976b53984 100644
--- a/engine/core/css/resolver/MediaQueryResult.h
+++ b/engine/core/css/resolver/MediaQueryResult.h
@@ -30,7 +30,7 @@
 namespace blink {
 
 class MediaQueryResult : public RefCounted<MediaQueryResult> {
-    WTF_MAKE_NONCOPYABLE(MediaQueryResult); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_NONCOPYABLE(MediaQueryResult); WTF_MAKE_FAST_ALLOCATED;
 public:
     MediaQueryResult(const MediaQueryExp& expr, bool result)
         : m_expression(expr)
diff --git a/engine/core/css/resolver/ScopedStyleResolver.h b/engine/core/css/resolver/ScopedStyleResolver.h
index da172380ecc..45edbcf36da 100644
--- a/engine/core/css/resolver/ScopedStyleResolver.h
+++ b/engine/core/css/resolver/ScopedStyleResolver.h
@@ -42,9 +42,9 @@ class StyleResolver;
 class StyleSheetContents;
 
 // This class selects a RenderStyle for a given element based on a collection of stylesheets.
-class ScopedStyleResolver final : public DummyBase<ScopedStyleResolver> {
+class ScopedStyleResolver final {
     WTF_MAKE_NONCOPYABLE(ScopedStyleResolver);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<ScopedStyleResolver> create(TreeScope& scope)
     {
diff --git a/engine/core/css/resolver/StyleResolver.cpp b/engine/core/css/resolver/StyleResolver.cpp
index 2fd53cfe8f4..41f47f5bf5e 100644
--- a/engine/core/css/resolver/StyleResolver.cpp
+++ b/engine/core/css/resolver/StyleResolver.cpp
@@ -459,11 +459,6 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
 
     state.fontBuilder().initForStyleResolve(state.document(), state.style());
 
-    bool needsCollection = false;
-    CSSDefaultStyleSheets::instance().ensureDefaultStyleSheetsForElement(element, needsCollection);
-    if (needsCollection)
-        collectFeatures();
-
     {
         ElementRuleCollector collector(state.elementContext(), state.style());
 
diff --git a/engine/core/css/resolver/StyleResolver.h b/engine/core/css/resolver/StyleResolver.h
index f0d7e0b974d..4f9052be2d5 100644
--- a/engine/core/css/resolver/StyleResolver.h
+++ b/engine/core/css/resolver/StyleResolver.h
@@ -92,8 +92,8 @@ public:
 };
 
 // This class selects a RenderStyle for a given element based on a collection of stylesheets.
-class StyleResolver final : public DummyBase<StyleResolver> {
-    WTF_MAKE_NONCOPYABLE(StyleResolver); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class StyleResolver final {
+    WTF_MAKE_NONCOPYABLE(StyleResolver); WTF_MAKE_FAST_ALLOCATED;
 public:
     explicit StyleResolver(Document&);
     virtual ~StyleResolver();
diff --git a/engine/core/dom/DOMSettableTokenList.h b/engine/core/dom/DOMSettableTokenList.h
index 6c603e49a51..7cbf47b84c4 100644
--- a/engine/core/dom/DOMSettableTokenList.h
+++ b/engine/core/dom/DOMSettableTokenList.h
@@ -42,7 +42,7 @@ class DOMSettableTokenList final
 #endif
     {
     DEFINE_WRAPPERTYPEINFO();
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<DOMSettableTokenList> create()
     {
diff --git a/engine/core/dom/DOMTokenList.h b/engine/core/dom/DOMTokenList.h
index a0bde334906..9aa2f33f2fe 100644
--- a/engine/core/dom/DOMTokenList.h
+++ b/engine/core/dom/DOMTokenList.h
@@ -35,9 +35,9 @@ namespace blink {
 class Element;
 class ExceptionState;
 
-class DOMTokenList : public DummyBase<DOMTokenList>, public ScriptWrappable {
+class DOMTokenList : public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
     WTF_MAKE_NONCOPYABLE(DOMTokenList);
 public:
     DOMTokenList()
diff --git a/engine/core/dom/Document.h b/engine/core/dom/Document.h
index 9a3abbdc52f..3c7cd76af5e 100644
--- a/engine/core/dom/Document.h
+++ b/engine/core/dom/Document.h
@@ -145,7 +145,7 @@ typedef unsigned char DocumentClassFlags;
 
 class Document;
 
-class DocumentVisibilityObserver : public DummyBase<void> {
+class DocumentVisibilityObserver {
 public:
     DocumentVisibilityObserver(Document&);
     virtual ~DocumentVisibilityObserver();
@@ -167,7 +167,6 @@ private:
 class Document : public ContainerNode, public TreeScope, public ExecutionContext, public ExecutionContextClient
     , public DocumentSupplementable, public LifecycleContext<Document>, public ResourceClient {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Document);
 public:
     static PassRefPtr<Document> create(const DocumentInit& initializer = DocumentInit())
     {
diff --git a/engine/core/dom/DocumentMarker.h b/engine/core/dom/DocumentMarker.h
index 745856bf803..c29bc14b377 100644
--- a/engine/core/dom/DocumentMarker.h
+++ b/engine/core/dom/DocumentMarker.h
@@ -35,7 +35,7 @@ class DocumentMarkerDetails;
 // It optionally includes a description that could be displayed in the user interface.
 // It also optionally includes a flag specifying whether the match is active, which is ignored
 // for all types other than type TextMatch.
-class DocumentMarker : public DummyBase<DocumentMarker> {
+class DocumentMarker {
 public:
     enum MarkerTypeIndex {
         SpellingMarkerIndex = 0,
diff --git a/engine/core/dom/DocumentMarkerController.h b/engine/core/dom/DocumentMarkerController.h
index 508bf08f07a..ff1097d3c83 100644
--- a/engine/core/dom/DocumentMarkerController.h
+++ b/engine/core/dom/DocumentMarkerController.h
@@ -51,8 +51,8 @@ private:
     Vector<String> m_words;
 };
 
-class DocumentMarkerController final : public DummyBase<DocumentMarkerController> {
-    WTF_MAKE_NONCOPYABLE(DocumentMarkerController); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class DocumentMarkerController final {
+    WTF_MAKE_NONCOPYABLE(DocumentMarkerController); WTF_MAKE_FAST_ALLOCATED;
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(DocumentMarkerController);
 public:
 
diff --git a/engine/core/dom/DocumentParser.h b/engine/core/dom/DocumentParser.h
index 4e83a12566b..bd2bd3ac7d3 100644
--- a/engine/core/dom/DocumentParser.h
+++ b/engine/core/dom/DocumentParser.h
@@ -86,7 +86,7 @@ private:
 
     // Every DocumentParser needs a pointer back to the document.
     // m_document will be 0 after the parser is stopped.
-    RawPtr<Document> m_document;
+    Document* m_document;
 };
 
 } // namespace blink
diff --git a/engine/core/dom/DocumentStyleSheetCollection.h b/engine/core/dom/DocumentStyleSheetCollection.h
index e2ad6518bb5..dc600062400 100644
--- a/engine/core/dom/DocumentStyleSheetCollection.h
+++ b/engine/core/dom/DocumentStyleSheetCollection.h
@@ -38,7 +38,7 @@ class TreeScope;
 
 class DocumentStyleSheetCollection final : public TreeScopeStyleSheetCollection {
     WTF_MAKE_NONCOPYABLE(DocumentStyleSheetCollection);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<DocumentStyleSheetCollection> create(TreeScope& treeScope)
     {
diff --git a/engine/core/dom/DocumentTest.cpp b/engine/core/dom/DocumentTest.cpp
index 8bd8b16a0ca..258878b1af1 100644
--- a/engine/core/dom/DocumentTest.cpp
+++ b/engine/core/dom/DocumentTest.cpp
@@ -56,10 +56,7 @@ void DocumentTest::SetUp()
     m_dummyPageHolder = DummyPageHolder::create(IntSize(800, 600));
 }
 
-class MockDocumentVisibilityObserver
-    : public DummyBase<MockDocumentVisibilityObserver>
-    , public DocumentVisibilityObserver {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(MockDocumentVisibilityObserver);
+class MockDocumentVisibilityObserver : public DocumentVisibilityObserver {
 public:
     static PassOwnPtr<MockDocumentVisibilityObserver> create(Document& document)
     {
diff --git a/engine/core/dom/ElementData.h b/engine/core/dom/ElementData.h
index bc025fb28df..101c4336387 100644
--- a/engine/core/dom/ElementData.h
+++ b/engine/core/dom/ElementData.h
@@ -47,7 +47,7 @@ class UniqueElementData;
 // ElementData represents very common, but not necessarily unique to an element,
 // data such as attributes, inline style, and parsed class names and ids.
 class ElementData : public RefCounted<ElementData> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     // Override RefCounted's deref() to ensure operator delete is called on
     // the appropriate subclass type.
diff --git a/engine/core/dom/ElementDataCache.h b/engine/core/dom/ElementDataCache.h
index 83719d2185d..d94a1f666a3 100644
--- a/engine/core/dom/ElementDataCache.h
+++ b/engine/core/dom/ElementDataCache.h
@@ -40,7 +40,7 @@ namespace blink {
 class Attribute;
 class ShareableElementData;
 
-class ElementDataCache final : public DummyBase<ElementDataCache>  {
+class ElementDataCache {
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(ElementDataCache)
 public:
     static PassOwnPtr<ElementDataCache> create() { return adoptPtr(new ElementDataCache); }
diff --git a/engine/core/dom/ExecutionContext.cpp b/engine/core/dom/ExecutionContext.cpp
index 691a91d93b2..40751dbfa7b 100644
--- a/engine/core/dom/ExecutionContext.cpp
+++ b/engine/core/dom/ExecutionContext.cpp
@@ -36,7 +36,7 @@
 
 namespace blink {
 
-class ExecutionContext::PendingException : public DummyBase<ExecutionContext::PendingException> {
+class ExecutionContext::PendingException {
     WTF_MAKE_NONCOPYABLE(PendingException);
 public:
     PendingException(const String& errorMessage, int lineNumber, int columnNumber, int scriptId, const String& sourceURL, PassRefPtr<ScriptCallStack> callStack)
diff --git a/engine/core/dom/IncrementLoadEventDelayCount.h b/engine/core/dom/IncrementLoadEventDelayCount.h
index b46be421002..d18d774f492 100644
--- a/engine/core/dom/IncrementLoadEventDelayCount.h
+++ b/engine/core/dom/IncrementLoadEventDelayCount.h
@@ -5,8 +5,8 @@
 #ifndef IncrementLoadEventDelayCount_h
 #define IncrementLoadEventDelayCount_h
 
-#include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
diff --git a/engine/core/dom/MutationObserverInterestGroup.h b/engine/core/dom/MutationObserverInterestGroup.h
index 1c7a37fd349..4e9eb61580e 100644
--- a/engine/core/dom/MutationObserverInterestGroup.h
+++ b/engine/core/dom/MutationObserverInterestGroup.h
@@ -41,7 +41,7 @@
 
 namespace blink {
 
-class MutationObserverInterestGroup final : public DummyBase<MutationObserverInterestGroup> {
+class MutationObserverInterestGroup final {
 public:
     static PassOwnPtr<MutationObserverInterestGroup> createForChildListMutation(Node& target)
     {
diff --git a/engine/core/dom/MutationObserverRegistration.h b/engine/core/dom/MutationObserverRegistration.h
index 688a31b3265..34a158c0901 100644
--- a/engine/core/dom/MutationObserverRegistration.h
+++ b/engine/core/dom/MutationObserverRegistration.h
@@ -41,7 +41,7 @@ namespace blink {
 
 class QualifiedName;
 
-class MutationObserverRegistration final : public DummyBase<MutationObserverRegistration> {
+class MutationObserverRegistration final {
 public:
     static PassOwnPtr<MutationObserverRegistration> create(MutationObserver&, Node*, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
     ~MutationObserverRegistration();
diff --git a/engine/core/dom/NodeRareData.h b/engine/core/dom/NodeRareData.h
index 32e5deb1680..3f34fc28b6b 100644
--- a/engine/core/dom/NodeRareData.h
+++ b/engine/core/dom/NodeRareData.h
@@ -31,9 +31,9 @@
 
 namespace blink {
 
-class NodeMutationObserverData final : public DummyBase<NodeMutationObserverData> {
+class NodeMutationObserverData final {
     WTF_MAKE_NONCOPYABLE(NodeMutationObserverData);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     Vector<OwnPtr<MutationObserverRegistration> > registry;
     HashSet<RawPtr<MutationObserverRegistration> > transientRegistry;
@@ -55,9 +55,9 @@ private:
     NodeMutationObserverData() { }
 };
 
-class NodeRareData : public DummyBase<NodeRareData>, public NodeRareDataBase {
+class NodeRareData : public NodeRareDataBase {
     WTF_MAKE_NONCOPYABLE(NodeRareData);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static NodeRareData* create(RenderObject* renderer)
     {
diff --git a/engine/core/dom/RequestAnimationFrameCallback.h b/engine/core/dom/RequestAnimationFrameCallback.h
index 33d033e8985..f5bb51a6e8b 100644
--- a/engine/core/dom/RequestAnimationFrameCallback.h
+++ b/engine/core/dom/RequestAnimationFrameCallback.h
@@ -35,7 +35,7 @@
 
 namespace blink {
 
-class RequestAnimationFrameCallback : public DummyBase<RequestAnimationFrameCallback> {
+class RequestAnimationFrameCallback {
 public:
     virtual ~RequestAnimationFrameCallback() { }
     virtual void trace(Visitor*) { }
diff --git a/engine/core/dom/ShadowTreeStyleSheetCollection.h b/engine/core/dom/ShadowTreeStyleSheetCollection.h
index 06c3ecec2b8..e10b67dd725 100644
--- a/engine/core/dom/ShadowTreeStyleSheetCollection.h
+++ b/engine/core/dom/ShadowTreeStyleSheetCollection.h
@@ -38,7 +38,7 @@ class StyleEngine;
 
 class ShadowTreeStyleSheetCollection final : public TreeScopeStyleSheetCollection {
     WTF_MAKE_NONCOPYABLE(ShadowTreeStyleSheetCollection);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     explicit ShadowTreeStyleSheetCollection(ShadowRoot&);
 
diff --git a/engine/core/dom/StyleElement.h b/engine/core/dom/StyleElement.h
index d812c9329c8..d2008616922 100644
--- a/engine/core/dom/StyleElement.h
+++ b/engine/core/dom/StyleElement.h
@@ -31,7 +31,7 @@ class Document;
 class Element;
 class TreeScope;
 
-class StyleElement : public DummyBase<void> {
+class StyleElement {
 public:
     StyleElement(Document*, bool createdByParser);
     virtual ~StyleElement();
diff --git a/engine/core/dom/StyleEngine.h b/engine/core/dom/StyleEngine.h
index 5db25b88362..591ffca7f91 100644
--- a/engine/core/dom/StyleEngine.h
+++ b/engine/core/dom/StyleEngine.h
@@ -53,7 +53,7 @@ class StyleSheet;
 class StyleSheetContents;
 
 class StyleEngine final : public CSSFontSelectorClient  {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
 
     class IgnoringPendingStylesheet : public TemporaryChange<bool> {
diff --git a/engine/core/dom/StyleSheetCollection.h b/engine/core/dom/StyleSheetCollection.h
index a8bfdc22cdb..6f26cc3ff52 100644
--- a/engine/core/dom/StyleSheetCollection.h
+++ b/engine/core/dom/StyleSheetCollection.h
@@ -38,9 +38,9 @@ namespace blink {
 class CSSStyleSheet;
 class StyleSheet;
 
-class StyleSheetCollection : public DummyBase<StyleSheetCollection> {
+class StyleSheetCollection {
     WTF_MAKE_NONCOPYABLE(StyleSheetCollection);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     friend class ActiveDocumentStyleSheetCollector;
     friend class ImportedDocumentStyleSheetCollector;
diff --git a/engine/core/dom/TreeScope.h b/engine/core/dom/TreeScope.h
index de22ffb2651..fdf303fcde6 100644
--- a/engine/core/dom/TreeScope.h
+++ b/engine/core/dom/TreeScope.h
@@ -44,7 +44,7 @@ class Node;
 // A class which inherits both Node and TreeScope must call clearRareData() in its destructor
 // so that the Node destructor no longer does problematic NodeList cache manipulation in
 // the destructor.
-class TreeScope : public DummyBase<void> {
+class TreeScope {
 public:
     TreeScope* parentTreeScope() const { return m_parentTreeScope; }
 
diff --git a/engine/core/dom/TreeShared.h b/engine/core/dom/TreeShared.h
index 13302843100..d2a844ce2fc 100644
--- a/engine/core/dom/TreeShared.h
+++ b/engine/core/dom/TreeShared.h
@@ -33,7 +33,7 @@ template<typename NodeType> class TreeShared;
 template<typename NodeType> void adopted(TreeShared<NodeType>*);
 #endif
 
-template<typename NodeType> class TreeShared : public DummyBase<NodeType> {
+template<typename NodeType> class TreeShared {
     WTF_MAKE_NONCOPYABLE(TreeShared);
 protected:
     TreeShared()
diff --git a/engine/core/dom/custom/CustomElementCallbackQueue.h b/engine/core/dom/custom/CustomElementCallbackQueue.h
index e49ded10130..bbed841c24c 100644
--- a/engine/core/dom/custom/CustomElementCallbackQueue.h
+++ b/engine/core/dom/custom/CustomElementCallbackQueue.h
@@ -44,7 +44,7 @@ namespace blink {
 
 // FIXME: Rename this because it contains resolution and upgrade as
 // well as callbacks.
-class CustomElementCallbackQueue : public DummyBase<CustomElementCallbackQueue> {
+class CustomElementCallbackQueue {
     WTF_MAKE_NONCOPYABLE(CustomElementCallbackQueue);
 public:
     static PassOwnPtr<CustomElementCallbackQueue> create(PassRefPtr<Element>);
diff --git a/engine/core/dom/custom/CustomElementMicrotaskDispatcher.h b/engine/core/dom/custom/CustomElementMicrotaskDispatcher.h
index 0bbd160ba9d..23473a35fc1 100644
--- a/engine/core/dom/custom/CustomElementMicrotaskDispatcher.h
+++ b/engine/core/dom/custom/CustomElementMicrotaskDispatcher.h
@@ -18,7 +18,7 @@ class CustomElementMicrotaskStep;
 class Document;
 class HTMLImportLoader;
 
-class CustomElementMicrotaskDispatcher final : public DummyBase<CustomElementMicrotaskDispatcher> {
+class CustomElementMicrotaskDispatcher final {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskDispatcher);
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CustomElementMicrotaskDispatcher);
 public:
diff --git a/engine/core/dom/custom/CustomElementMicrotaskRunQueue.cpp b/engine/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
index 9dcac28e77b..c2c28423703 100644
--- a/engine/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
+++ b/engine/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
@@ -15,8 +15,6 @@
 
 namespace blink {
 
-DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CustomElementMicrotaskRunQueue)
-
 CustomElementMicrotaskRunQueue::CustomElementMicrotaskRunQueue()
     : m_syncQueue(CustomElementSyncMicrotaskQueue::create())
     , m_asyncQueue(CustomElementAsyncImportMicrotaskQueue::create())
@@ -25,6 +23,10 @@ CustomElementMicrotaskRunQueue::CustomElementMicrotaskRunQueue()
 {
 }
 
+CustomElementMicrotaskRunQueue::~CustomElementMicrotaskRunQueue()
+{
+}
+
 void CustomElementMicrotaskRunQueue::enqueue(HTMLImportLoader* parentLoader, PassOwnPtr<CustomElementMicrotaskStep> step, bool importIsSync)
 {
     if (importIsSync) {
@@ -47,12 +49,6 @@ void CustomElementMicrotaskRunQueue::requestDispatchIfNeeded()
     m_dispatchIsPending = true;
 }
 
-void CustomElementMicrotaskRunQueue::trace(Visitor* visitor)
-{
-    visitor->trace(m_syncQueue);
-    visitor->trace(m_asyncQueue);
-}
-
 void CustomElementMicrotaskRunQueue::dispatch()
 {
     m_dispatchIsPending = false;
diff --git a/engine/core/dom/custom/CustomElementMicrotaskRunQueue.h b/engine/core/dom/custom/CustomElementMicrotaskRunQueue.h
index f445eee3df4..121222625d0 100644
--- a/engine/core/dom/custom/CustomElementMicrotaskRunQueue.h
+++ b/engine/core/dom/custom/CustomElementMicrotaskRunQueue.h
@@ -6,8 +6,9 @@
 #define CustomElementMicrotaskRunQueue_h
 
 #include "base/memory/weak_ptr.h"
-#include "platform/heap/Handle.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
 
 namespace blink {
 
@@ -17,16 +18,14 @@ class CustomElementMicrotaskStep;
 class HTMLImportLoader;
 
 class CustomElementMicrotaskRunQueue : public RefCounted<CustomElementMicrotaskRunQueue> {
-    DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CustomElementMicrotaskRunQueue)
 public:
     static PassRefPtr<CustomElementMicrotaskRunQueue> create() { return adoptRef(new CustomElementMicrotaskRunQueue()); }
+    ~CustomElementMicrotaskRunQueue();
 
     void enqueue(HTMLImportLoader* parentLoader, PassOwnPtr<CustomElementMicrotaskStep>, bool importIsSync);
     void requestDispatchIfNeeded();
     bool isEmpty() const;
 
-    void trace(Visitor*);
-
 private:
     CustomElementMicrotaskRunQueue();
 
diff --git a/engine/core/dom/custom/CustomElementMicrotaskStep.h b/engine/core/dom/custom/CustomElementMicrotaskStep.h
index 3ad2036ab85..50ae45dae80 100644
--- a/engine/core/dom/custom/CustomElementMicrotaskStep.h
+++ b/engine/core/dom/custom/CustomElementMicrotaskStep.h
@@ -36,7 +36,7 @@
 
 namespace blink {
 
-class CustomElementMicrotaskStep : public DummyBase<CustomElementMicrotaskStep> {
+class CustomElementMicrotaskStep {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskStep);
 public:
     CustomElementMicrotaskStep() { }
diff --git a/engine/core/dom/custom/CustomElementObserver.h b/engine/core/dom/custom/CustomElementObserver.h
index 2b2807d13b3..2f88bd693fa 100644
--- a/engine/core/dom/custom/CustomElementObserver.h
+++ b/engine/core/dom/custom/CustomElementObserver.h
@@ -38,7 +38,7 @@ namespace blink {
 
 class Element;
 
-class CustomElementObserver : public DummyBase<CustomElementObserver> {
+class CustomElementObserver {
 public:
     virtual ~CustomElementObserver() { }
 
diff --git a/engine/core/dom/custom/CustomElementScheduler.h b/engine/core/dom/custom/CustomElementScheduler.h
index b53d754d545..2d4479cd736 100644
--- a/engine/core/dom/custom/CustomElementScheduler.h
+++ b/engine/core/dom/custom/CustomElementScheduler.h
@@ -49,7 +49,7 @@ class Document;
 class Element;
 class HTMLImportChild;
 
-class CustomElementScheduler final : public DummyBase<CustomElementScheduler> {
+class CustomElementScheduler final {
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(CustomElementScheduler);
 public:
 
diff --git a/engine/core/dom/shadow/ElementShadow.h b/engine/core/dom/shadow/ElementShadow.h
index 046467e90cf..7aa3ded3cab 100644
--- a/engine/core/dom/shadow/ElementShadow.h
+++ b/engine/core/dom/shadow/ElementShadow.h
@@ -38,9 +38,9 @@
 
 namespace blink {
 
-class ElementShadow final : public DummyBase<ElementShadow> {
+class ElementShadow final {
     WTF_MAKE_NONCOPYABLE(ElementShadow);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<ElementShadow> create();
     ~ElementShadow();
diff --git a/engine/core/dom/shadow/ShadowRoot.h b/engine/core/dom/shadow/ShadowRoot.h
index 9dc61b46689..ef3185b10f7 100644
--- a/engine/core/dom/shadow/ShadowRoot.h
+++ b/engine/core/dom/shadow/ShadowRoot.h
@@ -45,7 +45,6 @@ class StyleSheetList;
 
 class ShadowRoot final : public DocumentFragment, public TreeScope, public DoublyLinkedListNode<ShadowRoot> {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ShadowRoot);
     friend class WTF::DoublyLinkedListNode<ShadowRoot>;
 public:
 
diff --git a/engine/core/dom/shadow/ShadowRootRareData.h b/engine/core/dom/shadow/ShadowRootRareData.h
index 4c2dbed6ab8..34f51048c6f 100644
--- a/engine/core/dom/shadow/ShadowRootRareData.h
+++ b/engine/core/dom/shadow/ShadowRootRareData.h
@@ -37,7 +37,7 @@
 
 namespace blink {
 
-class ShadowRootRareData : public DummyBase<ShadowRootRareData> {
+class ShadowRootRareData {
 public:
     ShadowRootRareData()
         : m_descendantShadowElementCount(0)
diff --git a/engine/core/editing/Caret.h b/engine/core/editing/Caret.h
index dc2b2f38dbc..d2b03866fe3 100644
--- a/engine/core/editing/Caret.h
+++ b/engine/core/editing/Caret.h
@@ -41,7 +41,7 @@ class RenderView;
 
 class CaretBase {
     WTF_MAKE_NONCOPYABLE(CaretBase);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 protected:
     enum CaretVisibility { Visible, Hidden };
     explicit CaretBase(CaretVisibility = Hidden);
@@ -75,9 +75,9 @@ private:
     CaretVisibility m_caretVisibility;
 };
 
-class DragCaretController final : public DummyBase<DragCaretController>, private CaretBase {
+class DragCaretController final : private CaretBase {
     WTF_MAKE_NONCOPYABLE(DragCaretController);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<DragCaretController> create();
 
diff --git a/engine/core/editing/EditingStyle.cpp b/engine/core/editing/EditingStyle.cpp
index b30e58bbf96..c26490fff4a 100644
--- a/engine/core/editing/EditingStyle.cpp
+++ b/engine/core/editing/EditingStyle.cpp
@@ -150,8 +150,8 @@ static bool hasTransparentBackgroundColor(CSSStyleDeclaration*);
 static bool hasTransparentBackgroundColor(StylePropertySet*);
 static PassRefPtr<CSSValue> backgroundColorInEffect(Node*);
 
-class HTMLElementEquivalent : public DummyBase<HTMLElementEquivalent> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class HTMLElementEquivalent {
+    WTF_MAKE_FAST_ALLOCATED;
     DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(HTMLElementEquivalent);
 public:
     static PassOwnPtr<HTMLElementEquivalent> create(CSSPropertyID propertyID, CSSValueID primitiveValue, const HTMLQualifiedName& tagName)
diff --git a/engine/core/editing/Editor.h b/engine/core/editing/Editor.h
index 5fbe67dad78..3cd623e97e9 100644
--- a/engine/core/editing/Editor.h
+++ b/engine/core/editing/Editor.h
@@ -58,7 +58,7 @@ class UndoStack;
 enum EditorCommandSource { CommandFromMenuOrKeyBinding, CommandFromDOM, CommandFromDOMWithUserInterface };
 enum EditorParagraphSeparator { EditorParagraphSeparatorIsDiv, EditorParagraphSeparatorIsP };
 
-class Editor final : public DummyBase<Editor> {
+class Editor final {
     WTF_MAKE_NONCOPYABLE(Editor);
 public:
     static PassOwnPtr<Editor> create(LocalFrame&);
diff --git a/engine/core/editing/FrameSelection.h b/engine/core/editing/FrameSelection.h
index 05a49ad4c22..1399c5851eb 100644
--- a/engine/core/editing/FrameSelection.h
+++ b/engine/core/editing/FrameSelection.h
@@ -56,10 +56,9 @@ enum RevealExtentOption {
     DoNotRevealExtent
 };
 
-class FrameSelection final : public DummyBase<FrameSelection>, public VisibleSelection::ChangeObserver, private CaretBase {
+class FrameSelection final : public VisibleSelection::ChangeObserver, private CaretBase {
     WTF_MAKE_NONCOPYABLE(FrameSelection);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(FrameSelection);
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<FrameSelection> create(LocalFrame* frame = 0)
     {
diff --git a/engine/core/editing/UndoStack.h b/engine/core/editing/UndoStack.h
index 4fada57b2d5..e784282cad9 100644
--- a/engine/core/editing/UndoStack.h
+++ b/engine/core/editing/UndoStack.h
@@ -40,7 +40,7 @@ namespace blink {
 class LocalFrame;
 class UndoStep;
 
-class UndoStack final : public DummyBase<UndoStack> {
+class UndoStack final {
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(UndoStack)
 public:
     static PassOwnPtr<UndoStack> create();
diff --git a/engine/core/editing/VisibleSelection.h b/engine/core/editing/VisibleSelection.h
index 9efcfa8d696..3c2666da434 100644
--- a/engine/core/editing/VisibleSelection.h
+++ b/engine/core/editing/VisibleSelection.h
@@ -117,7 +117,7 @@ public:
     // or end is moved to a different position.
     //
     // Objects implementing |ChangeObserver| interface must outlive the VisibleSelection object.
-    class ChangeObserver : public DummyBase<void> {
+    class ChangeObserver {
         WTF_MAKE_NONCOPYABLE(ChangeObserver);
     public:
         ChangeObserver();
diff --git a/engine/core/events/DOMWindowEventQueue.cpp b/engine/core/events/DOMWindowEventQueue.cpp
index 285c0703675..4b730064ca3 100644
--- a/engine/core/events/DOMWindowEventQueue.cpp
+++ b/engine/core/events/DOMWindowEventQueue.cpp
@@ -33,7 +33,7 @@
 
 namespace blink {
 
-class DOMWindowEventQueueTimer : public DummyBase<DOMWindowEventQueueTimer>, public SuspendableTimer {
+class DOMWindowEventQueueTimer : public SuspendableTimer {
     WTF_MAKE_NONCOPYABLE(DOMWindowEventQueueTimer);
 public:
     DOMWindowEventQueueTimer(DOMWindowEventQueue* eventQueue, ExecutionContext* context)
diff --git a/engine/core/events/EventFactory.h b/engine/core/events/EventFactory.h
index 8f52250d9ed..43494d43578 100644
--- a/engine/core/events/EventFactory.h
+++ b/engine/core/events/EventFactory.h
@@ -26,7 +26,7 @@
 #ifndef EventFactory_h
 #define EventFactory_h
 
-#include "platform/heap/Handle.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/text/AtomicString.h"
 
diff --git a/engine/core/events/EventPath.h b/engine/core/events/EventPath.h
index 1138fcc781e..0a1eb196ced 100644
--- a/engine/core/events/EventPath.h
+++ b/engine/core/events/EventPath.h
@@ -42,7 +42,7 @@ class TouchEvent;
 class TouchList;
 class TreeScope;
 
-class EventPath final : public DummyBase<EventPath> {
+class EventPath final {
 public:
     explicit EventPath(Event*);
     explicit EventPath(Node*);
diff --git a/engine/core/events/EventQueue.h b/engine/core/events/EventQueue.h
index 57bd76b40f8..8497c2eaa8d 100644
--- a/engine/core/events/EventQueue.h
+++ b/engine/core/events/EventQueue.h
@@ -36,7 +36,7 @@ namespace blink {
 
 class Event;
 
-class EventQueue : public DummyBase<EventQueue> {
+class EventQueue {
 public:
     virtual ~EventQueue() { }
     virtual void trace(Visitor*) { }
diff --git a/engine/core/events/EventTarget.h b/engine/core/events/EventTarget.h
index 8862adc7cd3..89152ca68fe 100644
--- a/engine/core/events/EventTarget.h
+++ b/engine/core/events/EventTarget.h
@@ -75,10 +75,7 @@ public:
 //   EventTarget directly).
 // - Figure out if you now need to inherit from ActiveDOMObject as well.
 // - In your class declaration, you will typically use
-//   REFCOUNTED_EVENT_TARGET(YourClassName) and
-//   WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(YourClassName). Make sure to include
-//   this header file in your .h file, or you will get very strange compiler
-//   errors.
+//   REFCOUNTED_EVENT_TARGET(YourClassName).
 // - Call ScriptWrappable::init(this) in your constructor, unless you are already
 //   doing so.
 // - Override EventTarget::interfaceName() and executionContext(). The former
@@ -89,7 +86,7 @@ public:
 //
 // Optionally, add a FooEvent.idl class, but that's outside the scope of this
 // comment (and much more straightforward).
-class EventTarget : public DummyBase<void>, public ScriptWrappable {
+class EventTarget : public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
 #if !ENABLE(OILPAN)
diff --git a/engine/core/events/GenericEventQueue.h b/engine/core/events/GenericEventQueue.h
index 3c7d54ec541..a22e9cbe36f 100644
--- a/engine/core/events/GenericEventQueue.h
+++ b/engine/core/events/GenericEventQueue.h
@@ -36,7 +36,7 @@
 namespace blink {
 
 class GenericEventQueue final : public EventQueue {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<GenericEventQueue> create(EventTarget*);
     virtual ~GenericEventQueue();
diff --git a/engine/core/fetch/MemoryCache.h b/engine/core/fetch/MemoryCache.h
index 6d19b4a893d..b8a0352896d 100644
--- a/engine/core/fetch/MemoryCache.h
+++ b/engine/core/fetch/MemoryCache.h
@@ -74,7 +74,7 @@ enum UpdateReason {
 // MemoryCacheEntry class is used only in MemoryCache class, but we don't make
 // MemoryCacheEntry class an inner class of MemoryCache because of dependency
 // from MemoryCacheLRUList.
-class MemoryCacheEntry final : public DummyBase<MemoryCacheEntry> {
+class MemoryCacheEntry final {
 public:
     static PassOwnPtr<MemoryCacheEntry> create(Resource* resource) { return adoptPtr(new MemoryCacheEntry(resource)); }
     void trace(Visitor*);
@@ -124,8 +124,8 @@ WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(blink::MemoryCacheLRUList);
 
 namespace blink {
 
-class MemoryCache final : public DummyBase<MemoryCache> {
-    WTF_MAKE_NONCOPYABLE(MemoryCache); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class MemoryCache final {
+    WTF_MAKE_NONCOPYABLE(MemoryCache); WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<MemoryCache> create();
     ~MemoryCache();
diff --git a/engine/core/fetch/Resource.h b/engine/core/fetch/Resource.h
index ce5f177b542..36954699cbe 100644
--- a/engine/core/fetch/Resource.h
+++ b/engine/core/fetch/Resource.h
@@ -51,8 +51,8 @@ class SharedBuffer;
 // A resource that is held in the cache. Classes who want to use this object should derive
 // from ResourceClient, to get the function calls in case the requested data has arrived.
 // This class also does the actual communication with the loader to obtain the resource from the network.
-class Resource : public DummyBase<Resource> {
-    WTF_MAKE_NONCOPYABLE(Resource); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class Resource {
+    WTF_MAKE_NONCOPYABLE(Resource); WTF_MAKE_FAST_ALLOCATED;
     friend class InspectorResource;
 
 public:
diff --git a/engine/core/fetch/ResourceFetcher.h b/engine/core/fetch/ResourceFetcher.h
index a65053d225a..35a6e3a0ca6 100644
--- a/engine/core/fetch/ResourceFetcher.h
+++ b/engine/core/fetch/ResourceFetcher.h
@@ -62,8 +62,7 @@ class ResourceLoaderSet;
 // are initialized without a LocalFrame), so a Document can keep a ResourceFetcher
 // alive past detach if scripts still reference the Document.
 class ResourceFetcher final : public RefCounted<ResourceFetcher>, public ResourceLoaderHost {
-    WTF_MAKE_NONCOPYABLE(ResourceFetcher); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ResourceFetcher);
+    WTF_MAKE_NONCOPYABLE(ResourceFetcher); WTF_MAKE_FAST_ALLOCATED;
 friend class ImageLoader;
 friend class ResourceCacheValidationSuppressor;
 
diff --git a/engine/core/fetch/ResourceLoaderHost.h b/engine/core/fetch/ResourceLoaderHost.h
index 5ca112b1839..207535c3dc7 100644
--- a/engine/core/fetch/ResourceLoaderHost.h
+++ b/engine/core/fetch/ResourceLoaderHost.h
@@ -45,7 +45,7 @@ class ResourceResponse;
 
 struct FetchInitiatorInfo;
 
-class ResourceLoaderHost : public DummyBase<void> {
+class ResourceLoaderHost {
 public:
     virtual void incrementRequestCount(const Resource*) = 0;
     virtual void decrementRequestCount(const Resource*) = 0;
diff --git a/engine/core/fetch/ResourceLoaderSet.h b/engine/core/fetch/ResourceLoaderSet.h
index d9fa662e900..936d661182f 100644
--- a/engine/core/fetch/ResourceLoaderSet.h
+++ b/engine/core/fetch/ResourceLoaderSet.h
@@ -36,7 +36,7 @@
 
 namespace blink {
 
-class ResourceLoaderSet final : public DummyBase<ResourceLoaderSet> {
+class ResourceLoaderSet final {
 public:
     typedef HashSet<RefPtr<ResourceLoader> > SetType;
 
diff --git a/engine/core/frame/EventHandlerRegistry.h b/engine/core/frame/EventHandlerRegistry.h
index 8a24920854f..d0863a54e10 100644
--- a/engine/core/frame/EventHandlerRegistry.h
+++ b/engine/core/frame/EventHandlerRegistry.h
@@ -7,6 +7,7 @@
 
 #include "core/frame/FrameHost.h"
 #include "wtf/HashCountedSet.h"
+#include "wtf/text/AtomicString.h"
 
 namespace blink {
 
@@ -18,7 +19,7 @@ typedef HashCountedSet<EventTarget*> EventTargetSet;
 // Registry for keeping track of event handlers. Note that only handlers on
 // documents that can be rendered or can receive input (i.e., are attached to a
 // FrameHost) are registered here.
-class EventHandlerRegistry final : public DummyBase<EventHandlerRegistry> {
+class EventHandlerRegistry final {
 public:
     explicit EventHandlerRegistry(FrameHost&);
     virtual ~EventHandlerRegistry();
diff --git a/engine/core/frame/Frame.h b/engine/core/frame/Frame.h
index 65fad04cf01..30f73456378 100644
--- a/engine/core/frame/Frame.h
+++ b/engine/core/frame/Frame.h
@@ -28,9 +28,9 @@
 #ifndef Frame_h
 #define Frame_h
 
-#include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
 
 namespace blink {
 class WebLayer;
diff --git a/engine/core/frame/FrameConsole.h b/engine/core/frame/FrameConsole.h
index 3bb2a2be917..b2d9d4e2d46 100644
--- a/engine/core/frame/FrameConsole.h
+++ b/engine/core/frame/FrameConsole.h
@@ -46,7 +46,7 @@ class ScriptCallStack;
 
 // FrameConsole takes per-frame console messages and routes them up through the FrameHost to the ChromeClient and Inspector.
 // It's meant as an abstraction around ChromeClient calls and the way that Blink core/ can add messages to the console.
-class FrameConsole final : public DummyBase<FrameConsole> {
+class FrameConsole final {
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(FrameConsole);
 public:
     static PassOwnPtr<FrameConsole> create(LocalFrame& frame)
diff --git a/engine/core/frame/FrameHost.h b/engine/core/frame/FrameHost.h
index a39322e28b0..5ed80433699 100644
--- a/engine/core/frame/FrameHost.h
+++ b/engine/core/frame/FrameHost.h
@@ -56,8 +56,8 @@ class Visitor;
 // browser-level concept and Blink core/ only knows about its LocalFrame (and FrameHost).
 // Separating Page from the rest of core/ through this indirection
 // allows us to slowly refactor Page without breaking the rest of core.
-class FrameHost final : public DummyBase<FrameHost> {
-    WTF_MAKE_NONCOPYABLE(FrameHost); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class FrameHost final {
+    WTF_MAKE_NONCOPYABLE(FrameHost); WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<FrameHost> create(Page&, ServiceProvider&);
     ~FrameHost();
@@ -82,7 +82,7 @@ public:
 private:
     FrameHost(Page&, ServiceProvider&);
 
-    RawPtr<Page> m_page;
+    Page* m_page;
     ServiceProvider& m_services;
     const OwnPtr<EventHandlerRegistry> m_eventHandlerRegistry;
 };
diff --git a/engine/core/frame/ImageBitmap.h b/engine/core/frame/ImageBitmap.h
index 22cf0e5806c..953ca59f12b 100644
--- a/engine/core/frame/ImageBitmap.h
+++ b/engine/core/frame/ImageBitmap.h
@@ -21,7 +21,6 @@ class ImageData;
 
 class ImageBitmap final : public RefCounted<ImageBitmap>, public ScriptWrappable, public ImageLoaderClient, public CanvasImageSource {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ImageBitmap);
 public:
     static PassRefPtr<ImageBitmap> create(HTMLImageElement*, const IntRect&);
     static PassRefPtr<ImageBitmap> create(HTMLCanvasElement*, const IntRect&);
diff --git a/engine/core/frame/LocalDOMWindow.h b/engine/core/frame/LocalDOMWindow.h
index 3c02d38f399..6b825d7f88f 100644
--- a/engine/core/frame/LocalDOMWindow.h
+++ b/engine/core/frame/LocalDOMWindow.h
@@ -83,7 +83,6 @@ enum SetLocationLocking { LockHistoryBasedOnGestureState, LockHistoryAndBackForw
 class LocalDOMWindow final : public RefCounted<LocalDOMWindow>, public EventTargetWithInlineData, public DOMWindowBase64, public FrameDestructionObserver, public Supplementable<LocalDOMWindow>, public LifecycleContext<LocalDOMWindow> {
     DEFINE_WRAPPERTYPEINFO();
     REFCOUNTED_EVENT_TARGET(LocalDOMWindow);
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(LocalDOMWindow);
 public:
     static PassRefPtr<LocalDOMWindow> create(LocalFrame& frame)
     {
diff --git a/engine/core/frame/Screen.h b/engine/core/frame/Screen.h
index f1dfc06d440..ed77538f0c1 100644
--- a/engine/core/frame/Screen.h
+++ b/engine/core/frame/Screen.h
@@ -43,7 +43,6 @@ class LocalFrame;
 
 class Screen final : public RefCounted<Screen>, public ScriptWrappable, public DOMWindowProperty, public Supplementable<Screen> {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Screen);
 public:
     static PassRefPtr<Screen> create(LocalFrame* frame)
     {
diff --git a/engine/core/html/HTMLCanvasElement.h b/engine/core/html/HTMLCanvasElement.h
index a1cf937e881..0bb453f056e 100644
--- a/engine/core/html/HTMLCanvasElement.h
+++ b/engine/core/html/HTMLCanvasElement.h
@@ -57,7 +57,7 @@ class ImageBuffer;
 class ImageBufferSurface;
 class IntSize;
 
-class CanvasObserver : public DummyBase<void> {
+class CanvasObserver {
     DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(CanvasObserver);
 public:
     virtual void canvasChanged(HTMLCanvasElement*, const FloatRect& changedRect) = 0;
@@ -69,7 +69,6 @@ public:
 
 class HTMLCanvasElement final : public HTMLElement, public DocumentVisibilityObserver, public CanvasImageSource, public ImageBufferClient {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(HTMLCanvasElement);
 public:
     DECLARE_NODE_FACTORY(HTMLCanvasElement);
     virtual ~HTMLCanvasElement();
diff --git a/engine/core/html/HTMLStyleElement.h b/engine/core/html/HTMLStyleElement.h
index c6e8656e6ab..7e6dc423bf4 100644
--- a/engine/core/html/HTMLStyleElement.h
+++ b/engine/core/html/HTMLStyleElement.h
@@ -35,7 +35,6 @@ typedef EventSender<HTMLStyleElement> StyleEventSender;
 
 class HTMLStyleElement final : public HTMLElement, private StyleElement {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(HTMLStyleElement);
 public:
     static PassRefPtr<HTMLStyleElement> create(Document&, bool createdByParser);
     virtual ~HTMLStyleElement();
diff --git a/engine/core/html/VoidCallback.h b/engine/core/html/VoidCallback.h
index db83bee9454..70cc8954670 100644
--- a/engine/core/html/VoidCallback.h
+++ b/engine/core/html/VoidCallback.h
@@ -30,7 +30,7 @@
 
 namespace blink {
 
-class VoidCallback : public DummyBase<VoidCallback> {
+class VoidCallback {
 public:
     virtual ~VoidCallback() { }
     virtual void trace(Visitor*) { }
diff --git a/engine/core/html/canvas/Canvas2DContextAttributes.h b/engine/core/html/canvas/Canvas2DContextAttributes.h
index 5c008bff299..3dda2451f90 100644
--- a/engine/core/html/canvas/Canvas2DContextAttributes.h
+++ b/engine/core/html/canvas/Canvas2DContextAttributes.h
@@ -30,6 +30,7 @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/CanvasContextAttributes.h"
 #include "wtf/PassRefPtr.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
diff --git a/engine/core/html/canvas/CanvasRenderingContext.h b/engine/core/html/canvas/CanvasRenderingContext.h
index 3aefa7bc9ba..1fcbcbe0e38 100644
--- a/engine/core/html/canvas/CanvasRenderingContext.h
+++ b/engine/core/html/canvas/CanvasRenderingContext.h
@@ -41,9 +41,9 @@ class HTMLCanvasElement;
 class KURL;
 class WebGLObject;
 
-class CanvasRenderingContext : public DummyBase<CanvasRenderingContext> {
+class CanvasRenderingContext {
     WTF_MAKE_NONCOPYABLE(CanvasRenderingContext);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     virtual ~CanvasRenderingContext() { }
 
diff --git a/engine/core/html/canvas/HitRegion.h b/engine/core/html/canvas/HitRegion.h
index b91d2802dba..4daf5e061d3 100644
--- a/engine/core/html/canvas/HitRegion.h
+++ b/engine/core/html/canvas/HitRegion.h
@@ -57,7 +57,7 @@ private:
     WindRule m_fillRule;
 };
 
-class HitRegionManager final : public DummyBase<HitRegionManager> {
+class HitRegionManager final {
     WTF_MAKE_NONCOPYABLE(HitRegionManager);
     DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(HitRegionManager)
 public:
diff --git a/engine/core/html/canvas/Path2D.h b/engine/core/html/canvas/Path2D.h
index 2d66987197e..f2d898f19a9 100644
--- a/engine/core/html/canvas/Path2D.h
+++ b/engine/core/html/canvas/Path2D.h
@@ -39,7 +39,7 @@ namespace blink {
 
 class Path2D final : public RefCounted<Path2D>, public CanvasPathMethods, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
     WTF_MAKE_NONCOPYABLE(Path2D);
 public:
     static PassRefPtr<Path2D> create() { return adoptRef(new Path2D); }
diff --git a/engine/core/html/canvas/WebGLContextObject.cpp b/engine/core/html/canvas/WebGLContextObject.cpp
index b8316704b9f..22b2d0f6912 100644
--- a/engine/core/html/canvas/WebGLContextObject.cpp
+++ b/engine/core/html/canvas/WebGLContextObject.cpp
@@ -71,10 +71,4 @@ blink::WebGraphicsContext3D* WebGLContextObject::getAWebGraphicsContext3D() cons
 #endif
 }
 
-void WebGLContextObject::trace(Visitor* visitor)
-{
-    visitor->trace(m_context);
-    WebGLObject::trace(visitor);
-}
-
 }
diff --git a/engine/core/html/canvas/WebGLContextObject.h b/engine/core/html/canvas/WebGLContextObject.h
index 48ebc553a3d..0dfde2f8d31 100644
--- a/engine/core/html/canvas/WebGLContextObject.h
+++ b/engine/core/html/canvas/WebGLContextObject.h
@@ -52,8 +52,6 @@ public:
 
     void detachContext();
 
-    virtual void trace(Visitor*) override;
-
 protected:
     explicit WebGLContextObject(WebGLRenderingContextBase*);
 
@@ -65,7 +63,7 @@ protected:
     virtual blink::WebGraphicsContext3D* getAWebGraphicsContext3D() const override final;
 
 private:
-    RawPtr<WebGLRenderingContextBase> m_context;
+    WebGLRenderingContextBase* m_context;
 #if ENABLE(OILPAN)
     RefPtr<WebGLSharedWebGraphicsContext3D> m_sharedWebGraphicsContext3D;
 #endif
diff --git a/engine/core/html/canvas/WebGLExtension.h b/engine/core/html/canvas/WebGLExtension.h
index 3c67f9377bf..4fd5f722eb3 100644
--- a/engine/core/html/canvas/WebGLExtension.h
+++ b/engine/core/html/canvas/WebGLExtension.h
@@ -34,7 +34,7 @@
 namespace blink {
 
 class WebGLExtension : public RefCounted<WebGLExtension> {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     WebGLRenderingContextBase* context() { return m_context; }
 
diff --git a/engine/core/html/canvas/WebGLFramebuffer.cpp b/engine/core/html/canvas/WebGLFramebuffer.cpp
index 01ab82369a2..d12d3ab2a63 100644
--- a/engine/core/html/canvas/WebGLFramebuffer.cpp
+++ b/engine/core/html/canvas/WebGLFramebuffer.cpp
@@ -29,6 +29,7 @@
 
 #include "core/html/canvas/WebGLRenderingContextBase.h"
 #include "platform/NotImplemented.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
@@ -43,8 +44,6 @@ namespace {
     public:
         static PassRefPtr<WebGLFramebuffer::WebGLAttachment> create(WebGLRenderbuffer*);
 
-        virtual void trace(Visitor*) override;
-
     private:
         explicit WebGLRenderbufferAttachment(WebGLRenderbuffer*);
         WebGLRenderbufferAttachment() { }
@@ -68,12 +67,6 @@ namespace {
         return adoptRef(new WebGLRenderbufferAttachment(renderbuffer));
     }
 
-    void WebGLRenderbufferAttachment::trace(Visitor* visitor)
-    {
-        visitor->trace(m_renderbuffer);
-        WebGLFramebuffer::WebGLAttachment::trace(visitor);
-    }
-
     WebGLRenderbufferAttachment::WebGLRenderbufferAttachment(WebGLRenderbuffer* renderbuffer)
         : m_renderbuffer(renderbuffer)
     {
@@ -151,8 +144,6 @@ namespace {
     public:
         static PassRefPtr<WebGLFramebuffer::WebGLAttachment> create(WebGLTexture*, GLenum target, GLint level);
 
-        virtual void trace(Visitor*) override;
-
     private:
         WebGLTextureAttachment(WebGLTexture*, GLenum target, GLint level);
         WebGLTextureAttachment() { }
@@ -178,12 +169,6 @@ namespace {
         return adoptRef(new WebGLTextureAttachment(texture, target, level));
     }
 
-    void WebGLTextureAttachment::trace(Visitor* visitor)
-    {
-        visitor->trace(m_texture);
-        WebGLFramebuffer::WebGLAttachment::trace(visitor);
-    }
-
     WebGLTextureAttachment::WebGLTextureAttachment(WebGLTexture* texture, GLenum target, GLint level)
         : m_texture(texture)
         , m_target(target)
@@ -628,12 +613,4 @@ GLenum WebGLFramebuffer::getDrawBuffer(GLenum drawBuffer)
     return GL_NONE;
 }
 
-void WebGLFramebuffer::trace(Visitor* visitor)
-{
-#if ENABLE(OILPAN)
-    visitor->trace(m_attachments);
-#endif
-    WebGLContextObject::trace(visitor);
-}
-
 }
diff --git a/engine/core/html/canvas/WebGLFramebuffer.h b/engine/core/html/canvas/WebGLFramebuffer.h
index 5507b7e5c45..43eece1dea4 100644
--- a/engine/core/html/canvas/WebGLFramebuffer.h
+++ b/engine/core/html/canvas/WebGLFramebuffer.h
@@ -29,8 +29,10 @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/WebGLContextObject.h"
 #include "core/html/canvas/WebGLSharedObject.h"
+#include "wtf/HashMap.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
@@ -59,8 +61,6 @@ public:
         virtual void attach(blink::WebGraphicsContext3D*, GLenum attachment) = 0;
         virtual void unattach(blink::WebGraphicsContext3D*, GLenum attachment) = 0;
 
-        virtual void trace(Visitor*) { }
-
     protected:
         WebGLAttachment();
     };
@@ -102,8 +102,6 @@ public:
 
     GLenum getDrawBuffer(GLenum);
 
-    virtual void trace(Visitor*) override;
-
 protected:
     explicit WebGLFramebuffer(WebGLRenderingContextBase*);
 
diff --git a/engine/core/html/canvas/WebGLProgram.cpp b/engine/core/html/canvas/WebGLProgram.cpp
index b8f99012ee3..e1085a20cd1 100644
--- a/engine/core/html/canvas/WebGLProgram.cpp
+++ b/engine/core/html/canvas/WebGLProgram.cpp
@@ -203,11 +203,4 @@ void WebGLProgram::cacheInfoIfNeeded()
     m_infoValid = true;
 }
 
-void WebGLProgram::trace(Visitor* visitor)
-{
-    visitor->trace(m_vertexShader);
-    visitor->trace(m_fragmentShader);
-    WebGLSharedObject::trace(visitor);
-}
-
 }
diff --git a/engine/core/html/canvas/WebGLProgram.h b/engine/core/html/canvas/WebGLProgram.h
index 5af658c339e..db5a235bbe0 100644
--- a/engine/core/html/canvas/WebGLProgram.h
+++ b/engine/core/html/canvas/WebGLProgram.h
@@ -60,8 +60,6 @@ public:
     bool attachShader(WebGLShader*);
     bool detachShader(WebGLShader*);
 
-    virtual void trace(Visitor*) override;
-
 protected:
     explicit WebGLProgram(WebGLRenderingContextBase*);
 
diff --git a/engine/core/html/canvas/WebGLRenderbuffer.h b/engine/core/html/canvas/WebGLRenderbuffer.h
index 534a556fe7c..22dab16d16a 100644
--- a/engine/core/html/canvas/WebGLRenderbuffer.h
+++ b/engine/core/html/canvas/WebGLRenderbuffer.h
@@ -29,6 +29,7 @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/WebGLSharedObject.h"
 #include "wtf/PassRefPtr.h"
+#include "wtf/RefPtr.h"
 
 namespace blink {
 
diff --git a/engine/core/html/canvas/WebGLRenderingContextBase.cpp b/engine/core/html/canvas/WebGLRenderingContextBase.cpp
index 4ad6d0140ed..4281a83d98f 100644
--- a/engine/core/html/canvas/WebGLRenderingContextBase.cpp
+++ b/engine/core/html/canvas/WebGLRenderingContextBase.cpp
@@ -492,8 +492,8 @@ private:
     RawPtr<WebGLRenderingContextBase> m_context;
 };
 
-class WebGLRenderingContextLostCallback final : public DummyBase<WebGLRenderingContextLostCallback>, public blink::WebGraphicsContext3D::WebGraphicsContextLostCallback {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class WebGLRenderingContextLostCallback final : public blink::WebGraphicsContext3D::WebGraphicsContextLostCallback {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<WebGLRenderingContextLostCallback> create(WebGLRenderingContextBase* context)
     {
@@ -516,8 +516,8 @@ private:
     RawPtr<WebGLRenderingContextBase> m_context;
 };
 
-class WebGLRenderingContextErrorMessageCallback final : public DummyBase<WebGLRenderingContextErrorMessageCallback>, public blink::WebGraphicsContext3D::WebGraphicsErrorMessageCallback {
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class WebGLRenderingContextErrorMessageCallback final : public blink::WebGraphicsContext3D::WebGraphicsErrorMessageCallback {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<WebGLRenderingContextErrorMessageCallback> create(WebGLRenderingContextBase* context)
     {
diff --git a/engine/core/html/canvas/WebGLRenderingContextBase.h b/engine/core/html/canvas/WebGLRenderingContextBase.h
index 00648a5597f..6a55fb7ee99 100644
--- a/engine/core/html/canvas/WebGLRenderingContextBase.h
+++ b/engine/core/html/canvas/WebGLRenderingContextBase.h
@@ -99,7 +99,6 @@ class WebGLRenderingContextLostCallback;
 class WebGLRenderingContextErrorMessageCallback;
 
 class WebGLRenderingContextBase: public CanvasRenderingContext, public ActiveDOMObject, public Page::MultisamplingChangedObserver {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WebGLRenderingContextBase);
 public:
     virtual ~WebGLRenderingContextBase();
 
@@ -573,7 +572,7 @@ protected:
         DraftExtension                  = 0x01,
     };
 
-    class ExtensionTracker : public DummyBase<ExtensionTracker> {
+    class ExtensionTracker {
     public:
         ExtensionTracker(ExtensionFlags flags, const char* const* prefixes)
             : m_draft(flags & DraftExtension)
diff --git a/engine/core/html/canvas/WebGLVertexArrayObjectOES.cpp b/engine/core/html/canvas/WebGLVertexArrayObjectOES.cpp
index fb7aab35154..cd46e238b3e 100644
--- a/engine/core/html/canvas/WebGLVertexArrayObjectOES.cpp
+++ b/engine/core/html/canvas/WebGLVertexArrayObjectOES.cpp
@@ -162,16 +162,4 @@ void WebGLVertexArrayObjectOES::setVertexAttribDivisor(GLuint index, GLuint divi
     state.divisor = divisor;
 }
 
-void WebGLVertexArrayObjectOES::VertexAttribState::trace(Visitor* visitor)
-{
-    visitor->trace(bufferBinding);
-}
-
-void WebGLVertexArrayObjectOES::trace(Visitor* visitor)
-{
-    visitor->trace(m_boundElementArrayBuffer);
-    visitor->trace(m_vertexAttribState);
-    WebGLContextObject::trace(visitor);
-}
-
 }
diff --git a/engine/core/html/canvas/WebGLVertexArrayObjectOES.h b/engine/core/html/canvas/WebGLVertexArrayObjectOES.h
index 1d91054ff41..502b54f028c 100644
--- a/engine/core/html/canvas/WebGLVertexArrayObjectOES.h
+++ b/engine/core/html/canvas/WebGLVertexArrayObjectOES.h
@@ -29,8 +29,9 @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/WebGLBuffer.h"
 #include "core/html/canvas/WebGLContextObject.h"
-#include "platform/heap/Handle.h"
+#include "wtf/RefCounted.h"
 #include "wtf/PassRefPtr.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
@@ -63,8 +64,6 @@ public:
         {
         }
 
-        void trace(Visitor*);
-
         bool enabled;
         RefPtr<WebGLBuffer> bufferBinding;
         GLsizei bytesPerElement;
@@ -90,8 +89,6 @@ public:
     void unbindBuffer(PassRefPtr<WebGLBuffer>);
     void setVertexAttribDivisor(GLuint index, GLuint divisor);
 
-    virtual void trace(Visitor*) override;
-
 private:
     WebGLVertexArrayObjectOES(WebGLRenderingContextBase*, VaoType);
 
diff --git a/engine/core/html/ime/InputMethodContext.h b/engine/core/html/ime/InputMethodContext.h
index f66f97d532b..477134d65db 100644
--- a/engine/core/html/ime/InputMethodContext.h
+++ b/engine/core/html/ime/InputMethodContext.h
@@ -45,9 +45,8 @@ class ExecutionContext;
 class InputMethodController;
 class Node;
 
-class InputMethodContext final : public DummyBase<InputMethodContext>, public EventTargetWithInlineData {
+class InputMethodContext final : public EventTargetWithInlineData {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(InputMethodContext);
 public:
     static PassOwnPtr<InputMethodContext> create(HTMLElement*);
     virtual ~InputMethodContext();
diff --git a/engine/core/html/imports/HTMLImport.h b/engine/core/html/imports/HTMLImport.h
index 2fbb19d884b..711a96256ca 100644
--- a/engine/core/html/imports/HTMLImport.h
+++ b/engine/core/html/imports/HTMLImport.h
@@ -94,7 +94,7 @@ class KURL;
 
 // The superclass of HTMLImportTreeRoot and HTMLImportChild
 // This represents the import tree data structure.
-class HTMLImport : public DummyBase<HTMLImport>, public TreeNode<HTMLImport> {
+class HTMLImport : public TreeNode<HTMLImport> {
 public:
     enum SyncMode {
         Sync  = 0,
diff --git a/engine/core/html/imports/HTMLImportChildClient.h b/engine/core/html/imports/HTMLImportChildClient.h
index 6ff97558e3d..b82d7b8c602 100644
--- a/engine/core/html/imports/HTMLImportChildClient.h
+++ b/engine/core/html/imports/HTMLImportChildClient.h
@@ -36,7 +36,7 @@ namespace blink {
 class HTMLImportChild;
 class Element;
 
-class HTMLImportChildClient : public DummyBase<void> {
+class HTMLImportChildClient {
 public:
     virtual ~HTMLImportChildClient() { }
     virtual void didFinish() = 0;
diff --git a/engine/core/html/imports/HTMLImportLoader.h b/engine/core/html/imports/HTMLImportLoader.h
index 49f464dd0dc..a799a6027e1 100644
--- a/engine/core/html/imports/HTMLImportLoader.h
+++ b/engine/core/html/imports/HTMLImportLoader.h
@@ -45,8 +45,7 @@ class Document;
 class HTMLImportChild;
 class HTMLImportsController;
 
-class HTMLImportLoader final : public DummyBase<HTMLImportLoader>,
-                               public MojoFetcher::Client {
+class HTMLImportLoader final : public MojoFetcher::Client {
 public:
     enum State {
         StateLoading,
diff --git a/engine/core/html/imports/HTMLImportsController.h b/engine/core/html/imports/HTMLImportsController.h
index 640e1f950b2..4e9622363b4 100644
--- a/engine/core/html/imports/HTMLImportsController.h
+++ b/engine/core/html/imports/HTMLImportsController.h
@@ -50,9 +50,8 @@ class HTMLImportChildClient;
 class HTMLImportLoader;
 class HTMLImportTreeRoot;
 
-class HTMLImportsController final : public DummyBase<HTMLImportsController>, public DocumentSupplement {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(HTMLImportsController);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class HTMLImportsController final : public DocumentSupplement {
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static const char* supplementName();
     static void provideTo(Document&);
diff --git a/engine/core/html/parser/HTMLTreeBuilder.h b/engine/core/html/parser/HTMLTreeBuilder.h
index 0c9d8ef57bb..bbadaf0ac15 100644
--- a/engine/core/html/parser/HTMLTreeBuilder.h
+++ b/engine/core/html/parser/HTMLTreeBuilder.h
@@ -50,8 +50,8 @@ class HTMLDocument;
 class Node;
 class HTMLDocumentParser;
 
-class HTMLTreeBuilder final : public DummyBase<HTMLTreeBuilder> {
-    WTF_MAKE_NONCOPYABLE(HTMLTreeBuilder); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class HTMLTreeBuilder final {
+    WTF_MAKE_NONCOPYABLE(HTMLTreeBuilder); WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<HTMLTreeBuilder> create(HTMLDocumentParser* parser, HTMLDocument* document, bool reportErrors)
     {
diff --git a/engine/core/inspector/ConsoleMessageStorage.h b/engine/core/inspector/ConsoleMessageStorage.h
index 9674d844fa4..c7959d94f20 100644
--- a/engine/core/inspector/ConsoleMessageStorage.h
+++ b/engine/core/inspector/ConsoleMessageStorage.h
@@ -14,9 +14,9 @@ namespace blink {
 
 class LocalDOMWindow;
 
-class ConsoleMessageStorage final : public DummyBase<ConsoleMessageStorage> {
+class ConsoleMessageStorage final {
     WTF_MAKE_NONCOPYABLE(ConsoleMessageStorage);
-    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<ConsoleMessageStorage> createForFrame(LocalFrame* frame)
     {
diff --git a/engine/core/loader/ImageLoader.h b/engine/core/loader/ImageLoader.h
index ef5951bbc82..b9c4629e39f 100644
--- a/engine/core/loader/ImageLoader.h
+++ b/engine/core/loader/ImageLoader.h
@@ -37,7 +37,7 @@ class IncrementLoadEventDelayCount;
 class FetchRequest;
 class Document;
 
-class ImageLoaderClient : public DummyBase<void> {
+class ImageLoaderClient {
 public:
     virtual void notifyImageSourceChanged() = 0;
 
@@ -57,7 +57,7 @@ class RenderImageResource;
 template<typename T> class EventSender;
 typedef EventSender<ImageLoader> ImageEventSender;
 
-class ImageLoader : public DummyBase<ImageLoader>, public ImageResourceClient {
+class ImageLoader : public ImageResourceClient {
 public:
     explicit ImageLoader(Element*);
     virtual ~ImageLoader();
diff --git a/engine/core/page/EventHandler.h b/engine/core/page/EventHandler.h
index 37fff903ddd..7bec910860a 100644
--- a/engine/core/page/EventHandler.h
+++ b/engine/core/page/EventHandler.h
@@ -81,7 +81,7 @@ typedef EventWithHitTestResults<PlatformMouseEvent> MouseEventWithHitTestResults
 enum AppendTrailingWhitespace { ShouldAppendTrailingWhitespace, DontAppendTrailingWhitespace };
 enum CheckDragHysteresis { ShouldCheckDragHysteresis, DontCheckDragHysteresis };
 
-class EventHandler : public DummyBase<EventHandler> {
+class EventHandler {
     WTF_MAKE_NONCOPYABLE(EventHandler);
 public:
     explicit EventHandler(LocalFrame*);
diff --git a/engine/core/page/Page.h b/engine/core/page/Page.h
index a725665301f..ab3028416ff 100644
--- a/engine/core/page/Page.h
+++ b/engine/core/page/Page.h
@@ -65,8 +65,7 @@ typedef uint64_t LinkHash;
 
 float deviceScaleFactor(LocalFrame*);
 
-class Page final : public DummyBase<Page>, public Supplementable<Page>, public LifecycleContext<Page>, public SettingsDelegate {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Page);
+class Page final : public Supplementable<Page>, public LifecycleContext<Page>, public SettingsDelegate {
     WTF_MAKE_NONCOPYABLE(Page);
     friend class Settings;
 public:
@@ -145,7 +144,7 @@ public:
 
     double timerAlignmentInterval() const;
 
-    class MultisamplingChangedObserver : public DummyBase<void> {
+    class MultisamplingChangedObserver {
     public:
         virtual void multisamplingChanged(bool) = 0;
     };
diff --git a/engine/core/rendering/RenderObject.h b/engine/core/rendering/RenderObject.h
index 577ae5b1b69..20ae860aad4 100644
--- a/engine/core/rendering/RenderObject.h
+++ b/engine/core/rendering/RenderObject.h
@@ -142,7 +142,7 @@ const int showTreeCharacterOffset = 39;
 #endif
 
 // Base class for all rendering tree objects.
-class RenderObject : public DummyBase<RenderObject>, public ImageResourceClient {
+class RenderObject : public ImageResourceClient {
     friend class RenderBlock;
     friend class RenderBlockFlow;
     friend class RenderLayerScrollableArea; // For setParent.
diff --git a/engine/core/rendering/RenderObjectChildList.cpp b/engine/core/rendering/RenderObjectChildList.cpp
index 653011fd35f..c084f465128 100644
--- a/engine/core/rendering/RenderObjectChildList.cpp
+++ b/engine/core/rendering/RenderObjectChildList.cpp
@@ -33,12 +33,6 @@
 
 namespace blink {
 
-void RenderObjectChildList::trace(Visitor* visitor)
-{
-    visitor->trace(m_firstChild);
-    visitor->trace(m_lastChild);
-}
-
 void RenderObjectChildList::destroyLeftoverChildren()
 {
     while (firstChild()) {
diff --git a/engine/core/rendering/RenderObjectChildList.h b/engine/core/rendering/RenderObjectChildList.h
index 3fd1b9cd571..33e9a9823e7 100644
--- a/engine/core/rendering/RenderObjectChildList.h
+++ b/engine/core/rendering/RenderObjectChildList.h
@@ -41,10 +41,9 @@ public:
         , m_lastChild(nullptr)
     {
     }
-    void trace(Visitor*);
 
-    RenderObject* firstChild() const { return m_firstChild.get(); }
-    RenderObject* lastChild() const { return m_lastChild.get(); }
+    RenderObject* firstChild() const { return m_firstChild; }
+    RenderObject* lastChild() const { return m_lastChild; }
 
     // FIXME: Temporary while RenderBox still exists. Eventually this will just happen during insert/append/remove methods on the child list, and nobody
     // will need to manipulate firstChild or lastChild directly.
@@ -61,8 +60,8 @@ public:
     }
 
 private:
-    RawPtr<RenderObject> m_firstChild;
-    RawPtr<RenderObject> m_lastChild;
+    RenderObject* m_firstChild;
+    RenderObject* m_lastChild;
 };
 
 } // namespace blink
diff --git a/engine/core/rendering/RenderSelectionInfo.h b/engine/core/rendering/RenderSelectionInfo.h
index 5bed01933d6..4346c229bb0 100644
--- a/engine/core/rendering/RenderSelectionInfo.h
+++ b/engine/core/rendering/RenderSelectionInfo.h
@@ -30,8 +30,8 @@
 
 namespace blink {
 
-class RenderSelectionInfoBase : public DummyBase<RenderSelectionInfoBase> {
-    WTF_MAKE_NONCOPYABLE(RenderSelectionInfoBase); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+class RenderSelectionInfoBase {
+    WTF_MAKE_NONCOPYABLE(RenderSelectionInfoBase); WTF_MAKE_FAST_ALLOCATED;
 public:
     RenderSelectionInfoBase()
         : m_object(nullptr)
diff --git a/engine/core/testing/NullExecutionContext.h b/engine/core/testing/NullExecutionContext.h
index 6e3fc5686ff..e801f039e1c 100644
--- a/engine/core/testing/NullExecutionContext.h
+++ b/engine/core/testing/NullExecutionContext.h
@@ -14,7 +14,6 @@
 namespace blink {
 
 class NullExecutionContext final : public RefCounted<NullExecutionContext>, public ExecutionContext {
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(NullExecutionContext);
 public:
     NullExecutionContext();
 
diff --git a/engine/platform/Timer.h b/engine/platform/Timer.h
index 0dc1bc9e6f7..167c4fccf4c 100644
--- a/engine/platform/Timer.h
+++ b/engine/platform/Timer.h
@@ -38,7 +38,7 @@ namespace blink {
 // Time intervals are all in seconds.
 
 class PLATFORM_EXPORT TimerBase {
-    WTF_MAKE_NONCOPYABLE(TimerBase); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
+    WTF_MAKE_NONCOPYABLE(TimerBase); WTF_MAKE_FAST_ALLOCATED;
 public:
     TimerBase();
     virtual ~TimerBase();
diff --git a/engine/platform/graphics/gpu/Extensions3DUtil.cpp b/engine/platform/graphics/gpu/Extensions3DUtil.cpp
index 01fa4ab1533..fbedbae3c12 100644
--- a/engine/platform/graphics/gpu/Extensions3DUtil.cpp
+++ b/engine/platform/graphics/gpu/Extensions3DUtil.cpp
@@ -6,6 +6,7 @@
 #include "platform/graphics/gpu/Extensions3DUtil.h"
 
 #include "public/platform/WebGraphicsContext3D.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/text/CString.h"
 #include "wtf/text/StringHash.h"
 
diff --git a/engine/platform/heap/Handle.h b/engine/platform/heap/Handle.h
index 41e044c0e5a..cb5dad025e5 100644
--- a/engine/platform/heap/Handle.h
+++ b/engine/platform/heap/Handle.h
@@ -31,17 +31,8 @@
 #ifndef Handle_h
 #define Handle_h
 
-#include "wtf/HashFunctions.h"
-#include "wtf/PassOwnPtr.h"
-#include "wtf/RawPtr.h"
-#include "wtf/RefCounted.h"
-#include "wtf/TypeTraits.h"
-#include "wtf/text/AtomicString.h"
+#include "wtf/StdLibExtras.h"
 
-// Classes that contain heap references but aren't themselves heap
-// allocated, have some extra macros available which allows their use
-// to be restricted to cases where the garbage collector is able
-// to discover their heap references.
 //
 // STACK_ALLOCATED(): Use if the object is only stack allocated. Heap objects
 // should be in Members but you do not need the trace method as they are on
@@ -98,10 +89,6 @@ namespace blink {
 
 class Visitor {
 public:
-    template<typename T>
-    void mark(T* t)
-    {
-    }
     template<typename T>
     void trace(const T* t)
     {
@@ -116,16 +103,6 @@ public:
     }
 };
 
-#define WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(TYPE)
-
-template<typename T>
-class DummyBase {
-public:
-    DummyBase() { }
-    ~DummyBase() { }
-};
-
-#define WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED WTF_MAKE_FAST_ALLOCATED
 #define DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(type) \
     public:                                            \
         ~type();                                       \
diff --git a/engine/platform/image-decoders/ImageDecoder.h b/engine/platform/image-decoders/ImageDecoder.h
index 945e6050288..eaebaf2dc4f 100644
--- a/engine/platform/image-decoders/ImageDecoder.h
+++ b/engine/platform/image-decoders/ImageDecoder.h
@@ -35,6 +35,7 @@
 #include "platform/image-decoders/ImageFrame.h"
 #include "public/platform/Platform.h"
 #include "wtf/Assertions.h"
+#include "wtf/PassOwnPtr.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Threading.h"
 #include "wtf/Vector.h"
diff --git a/engine/wtf/ListHashSet.h b/engine/wtf/ListHashSet.h
index 52b2906becf..1b8515a5798 100644
--- a/engine/wtf/ListHashSet.h
+++ b/engine/wtf/ListHashSet.h
@@ -396,26 +396,6 @@ namespace WTF {
             allocator->deallocate(this);
         }
 
-        // This is not called in normal tracing, but it is called if we find a
-        // pointer to a node on the stack using conservative scanning. Since
-        // the original ListHashSet may no longer exist we make sure to mark
-        // the neighbours in the chain too.
-        void trace(typename NodeAllocator::Visitor* visitor)
-        {
-            // The conservative stack scan can find nodes that have been
-            // removed from the set and destructed. We don't need to trace
-            // these, and it would be wrong to do so, because the class will
-            // not expect the trace method to be called after the destructor.
-            // It's an error to remove a node from the ListHashSet while an
-            // iterator is positioned at that node, so there should be no valid
-            // pointers from the stack to a destructed node.
-            if (wasAlreadyDestructed())
-                return;
-            NodeAllocator::traceValue(visitor, this);
-            visitor->mark(next());
-            visitor->mark(prev());
-        }
-
         ListHashSetNode* next() const { return reinterpret_cast<ListHashSetNode*>(this->m_next); }
         ListHashSetNode* prev() const { return reinterpret_cast<ListHashSetNode*>(this->m_prev); }