Add Instrumentation class (#22650)

lib/web_ui/lib/src/engine/canvaskit/canvaskit_api.dart

@@ -1801,6 +1801,11 @@ class ProductionCollector implements Collector {
 
   @override
   void register(Object wrapper, SkDeletable deletable) {
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${deletable.constructor.name} registered',
+      );
+    }
     _skObjectFinalizationRegistry.register(wrapper, deletable);
   }
 
@@ -1859,6 +1864,11 @@ class ProductionCollector implements Collector {
         // again if the objects is worth collecting.
         continue;
       }
+      if (Instrumentation.enabled) {
+        Instrumentation.instance.incrementCounter(
+          '${deletable.constructor.name} deleted',
+        );
+      }
       try {
         deletable.delete();
       } catch (error, stackTrace) {
@@ -1907,6 +1917,21 @@ class SkDeletable {
 
   /// Returns whether the correcponding C++ object has been deleted.
   external bool isDeleted();
+
+  /// Returns the JavaScript constructor for this object.
+  ///
+  /// This is useful for debugging.
+  external JsConstructor get constructor;
+}
+
+@JS()
+@anonymous
+class JsConstructor {
+  /// The name of the "constructor", typically the function name called with
+  /// the `new` keyword, or the ES6 class name.
+  ///
+  /// This is useful for debugging.
+  external String get name;
 }
 
 /// Attaches a weakly referenced object to another object and calls a finalizer

lib/web_ui/lib/src/engine/canvaskit/skia_object_cache.dart

@@ -147,6 +147,11 @@ abstract class ManagedSkiaObject<T extends Object> extends SkiaObject<T> {
     } else {
       // If FinalizationRegistry is _not_ supported we may need to delete
       // and resurrect the object multiple times before deleting it forever.
+      if (Instrumentation.enabled) {
+        Instrumentation.instance.incrementCounter(
+          '${(defaultObject as SkDeletable).constructor.name} created',
+        );
+      }
       if (isResurrectionExpensive) {
         SkiaObjects.manageExpensive(this);
       } else {
@@ -161,6 +166,11 @@ abstract class ManagedSkiaObject<T extends Object> extends SkiaObject<T> {
   T _doResurrect() {
     assert(!browserSupportsFinalizationRegistry);
     final T skiaObject = resurrect();
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${(skiaObject as SkDeletable).constructor.name} resurrected',
+      );
+    }
     rawSkiaObject = skiaObject;
     if (isResurrectionExpensive) {
       SkiaObjects.manageExpensive(this);
@@ -173,6 +183,11 @@ abstract class ManagedSkiaObject<T extends Object> extends SkiaObject<T> {
   @override
   void didDelete() {
     assert(!browserSupportsFinalizationRegistry);
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${(rawSkiaObject as SkDeletable).constructor.name} deleted',
+      );
+    }
     rawSkiaObject = null;
   }
 
@@ -303,6 +318,11 @@ class SkiaObjectBox<R extends StackTraceDebugger, T extends Object> extends Skia
 
   void _initialize(R debugReferrer, T initialValue) {
     _update(initialValue);
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${_skDeletable?.constructor.name} created',
+      );
+    }
     if (assertionsEnabled) {
       debugReferrers.add(debugReferrer);
     }
@@ -355,6 +375,11 @@ class SkiaObjectBox<R extends StackTraceDebugger, T extends Object> extends Skia
     assert(_resurrector != null);
     assert(!_isDeletedPermanently, 'Cannot use deleted object.');
     _update(_resurrector!());
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${_skDeletable?.constructor.name} resurrected',
+      );
+    }
     SkiaObjects.manageExpensive(this);
     return skiaObject;
   }
@@ -366,6 +391,11 @@ class SkiaObjectBox<R extends StackTraceDebugger, T extends Object> extends Skia
 
   @override
   void didDelete() {
+    if (Instrumentation.enabled) {
+      Instrumentation.instance.incrementCounter(
+        '${_skDeletable?.constructor.name} deleted',
+      );
+    }
     assert(!browserSupportsFinalizationRegistry);
     _update(null);
   }
@@ -419,7 +449,8 @@ class SkiaObjectBox<R extends StackTraceDebugger, T extends Object> extends Skia
         if (browserSupportsFinalizationRegistry) {
           Collector.instance.collect(_skDeletable!);
         } else {
-          _skDeletable!.delete();
+          delete();
+          didDelete();
         }
       }
       rawSkiaObject = null;

lib/web_ui/lib/src/engine/profiler.dart

@@ -218,3 +218,66 @@ void _frameTimingsOnRasterFinish() {
 int _nowMicros() {
   return (html.window.performance.now() * 1000).toInt();
 }
+
+/// Counts various events that take place while the app is running.
+///
+/// This class will slow down the app, and therefore should be disabled while
+/// benchmarking. For example, avoid using it in conjunction with [Profiler].
+class Instrumentation {
+  Instrumentation._() {
+    _checkInstrumentationEnabled();
+  }
+
+  /// Whether instrumentation is enabled.
+  ///
+  /// Check this value before calling any other methods in this class.
+  static const bool enabled = const bool.fromEnvironment(
+    'FLUTTER_WEB_ENABLE_INSTRUMENTATION',
+    defaultValue: false,
+  );
+
+  /// Returns the singleton that provides instrumentation API.
+  static Instrumentation get instance {
+    _checkInstrumentationEnabled();
+    return _instance;
+  }
+
+  static late final Instrumentation _instance = Instrumentation._();
+
+  static void _checkInstrumentationEnabled() {
+    if (!enabled) {
+      throw Exception(
+        'Cannot use Instrumentation unless it is enabled. '
+        'You can enable it by setting the `FLUTTER_WEB_ENABLE_INSTRUMENTATION` '
+        'environment variable to true, or by passing '
+        '--dart-define=FLUTTER_WEB_ENABLE_INSTRUMENTATION=true to the flutter '
+        'tool.',
+      );
+    }
+  }
+
+  final Map<String, int> _counters = <String, int>{};
+  Timer? _printTimer;
+
+  /// Increments the count of a particular event by one.
+  void incrementCounter(String event) {
+    _checkInstrumentationEnabled();
+    final int currentCount = _counters[event] ?? 0;
+    _counters[event] = currentCount + 1;
+    _printTimer ??= Timer(
+      const Duration(seconds: 2),
+      () {
+        final StringBuffer message = StringBuffer('Engine counters:\n');
+        final List<MapEntry<String, int>> entries = _counters.entries.toList()
+          ..sort((MapEntry<String, int> a, MapEntry<String, int> b) {
+            return a.key.compareTo(b.key);
+          });
+        for (MapEntry<String, int> entry in entries) {
+          message.writeln('  ${entry.key}: ${entry.value}');
+        }
+        print(message);
+        _printTimer = null;
+      },
+    );
+  }
+}

lib/web_ui/test/canvaskit/skia_objects_cache_test.dart

@@ -292,6 +292,9 @@ class TestSkDeletable implements SkDeletable {
     _isDeleted = true;
     deleteCount++;
   }
+
+  @override
+  JsConstructor get constructor => TestJsConstructor('TestSkDeletable');
 }
 
 class TestOneShotSkiaObject extends OneShotSkiaObject<SkPaint> implements SkDeletable {
@@ -310,6 +313,16 @@ class TestOneShotSkiaObject extends OneShotSkiaObject<SkPaint> implements SkDele
     rawSkiaObject?.delete();
     deleteCount++;
   }
+
+  @override
+  JsConstructor get constructor => TestJsConstructor('TestOneShotSkiaObject');
+}
+
+class TestJsConstructor implements JsConstructor{
+  TestJsConstructor(this.name);
+
+  @override
+  final String name;
 }
 
 class TestSkiaObject extends ManagedSkiaObject<SkPaint> {