Specs: define how importing element registrations works, move built-in elements to a separate module so dart:sky can be a simple library

Review URL: https://codereview.chromium.org/944873007

specs/elements.md

@@ -2,10 +2,6 @@ Sky DOM APIs
 ============
 
 ```dart
-SKY MODULE
-<!-- part of dart:sky -->
-
-<script>
 // ELEMENT TREE API
 
 abstract class Node extends EventTarget {
@@ -278,108 +274,6 @@ class ApplicationRoot extends Root {
 
 Type rootLayoutManager = BlockLayoutManager; // O(1)
 
-
-// BUILT-IN ELEMENTS
-
-@tagname('import')
-class ImportElement extends Element {
-  ImportElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('template')
-class TemplateElement extends Element {
-  TemplateElement = Element;
-
-  // TODO(ianh): convert <template> to using a token stream instead of a Fragment
-
-  external Fragment get content; // O(1)
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('script')
-class ScriptElement extends Element {
-  ScriptElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('style')
-class StyleElement extends Element {
-  StyleElement = Element;
-
-  external List<Rule> getRules(); // O(N) in rules
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('content')
-class ContentElement extends Element {
-  ContentElement = Element;
-
-  external List<Node> getDistributedNodes(); // O(N) in distributed nodes
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-@tagname('img')
-class ImgElement extends Element {
-  ImgElement = Element;
-
-  @override
-  Type getLayoutManager() => ImgElementLayoutManager; // O(1)
-}
-
-@tagname('div')
-class DivElement extends Element {
-  DivElement = Element;
-}
-
-@tagname('span')
-class SpanElement extends Element {
-  SpanElement = Element;
-}
-
-@tagname('iframe')
-class IframeElement extends Element {
-  IframeElement = Element;
-
-  @override
-  Type getLayoutManager() => IframeElementLayoutManager; // O(1)
-}
-
-@tagname('t')
-class TElement extends Element {
-  TElement = Element;
-}
-
-@tagname('a')
-class AElement extends Element {
-  AElement = Element;
-}
-
-@tagname('title')
-class TitleElement extends Element {
-  TitleElement = Element;
-
-  @override
-  Type getLayoutManager() => null; // O(1)
-}
-
-class _ErrorElement extends Element {
-  _ErrorElement._create();
-
-  @override
-  Type getLayoutManager() => _ErrorElementLayoutManager; // O(1)
-}
-
 class SelectorQuery {
   external SelectorQuery(String selector); // O(F()) where F() is the complexity of the selector
 
@@ -391,5 +285,4 @@ class SelectorQuery {
   //  - Fragment
   //  - Root
 }
-</script>
 ```

specs/events.md

@@ -2,10 +2,6 @@ Sky Event Model
 ===============
 
 ```dart
-SKY MODULE
-<!-- part of dart:sky -->
-
-<script>
 import 'dart:collection';
 import 'dart:async';
 
@@ -199,5 +195,4 @@ class EventTarget {
     _eventsController.add(event);
   }
 }
-</script>
 ```

specs/gestures.md

@@ -2,10 +2,6 @@ Gestures
 ========
 
 ```dart
-SKY MODULE
-<!-- part of dart:sky -->
-
-<script>
 abstract class GestureEvent extends Event {
   Gesture _gesture;
   Gesture get gesture => _gesture;
@@ -253,7 +249,6 @@ class GestureManager {
 
 }
 /*
-</script>
 ```
 
 Gestures defined in the framework

specs/modules.md

@@ -31,21 +31,36 @@ imported module:
 <import src="path/to/chocolate.sky" as="chocolate" />
 ```
 
+Each module implicitly imports the [Built-In Elements
+Module](builtins.md).
+
+When a module imports another, and the ``import`` element has no
+``as`` attribute, then any elements registered in that module whose
+tag names do not begin with an underscore must be registered on the
+importing module. (If multiple elements are registered with the same
+name, that name gets marked as dead for that module and all the
+registrations for that name are discarded.)
+
+TODO(ianh): decide if elements imported with "as" should be imported
+but with the "as" name prefixed, as in ``<foo.button>``
+
 
 Module API
 ----------
 
 Each module consists of one or more libraries. The first library in a
-module is the *element tree library*, which imports the dart:sky
-module and then consists of the following code for a Sky module:
+module is the *element tree library*, which consists of the following
+code for a Sky module:
 
 ```dart
+import 'dart:sky';
 final Module module = new Module();
 ```
 
 ...and the following code for a Sky application:
 
 ```dart
+import 'dart:sky';
 final Module module = new Application();
 ```