Adding a mechanism to 'upgrade' the Dart type of elements

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 3cc7cd5c47e8b433f1f15063696c152a3b32233e..f323780bc337e781a41388d669b95342ff89bb5f 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -14872,32 +14872,6 @@ class HtmlDocument extends Document {
    * This custom element can also be instantiated via HTML using the syntax
    * `<input is="x-bar"></input>`
    *
-   * The [nativeTagName] parameter is needed by platforms without native support
-   * when subclassing a native type other than:
-   *
-   * * HtmlElement
-   * * SvgElement
-   * * AnchorElement
-   * * AudioElement
-   * * ButtonElement
-   * * CanvasElement
-   * * DivElement
-   * * ImageElement
-   * * InputElement
-   * * LIElement
-   * * LabelElement
-   * * MenuElement
-   * * MeterElement
-   * * OListElement
-   * * OptionElement
-   * * OutputElement
-   * * ParagraphElement
-   * * PreElement
-   * * ProgressElement
-   * * SelectElement
-   * * SpanElement
-   * * UListElement
-   * * VideoElement
    */
   void register(String tag, Type customElementClass, {String extendsTag}) {
     _Utils.register(this, tag, customElementClass, extendsTag);
@@ -14928,6 +14902,28 @@ class HtmlDocument extends Document {
   @Experimental()
   Stream<Event> get onVisibilityChange =>
       visibilityChangeEvent.forTarget(this);
+
+  /// Creates an element upgrader which can be used to change the Dart wrapper
+  /// type for elements.
+  ///
+  /// The type specified must be a subclass of HtmlElement, when an element is
+  /// upgraded then the created constructor will be invoked on that element.
+  ///
+  /// If the type is not a direct subclass of HtmlElement then the extendsTag
+  /// parameter must be provided.
+  @Experimental()
+  ElementUpgrader createElementUpgrader(Type type, {String extendsTag}) {
+    return new _VMElementUpgrader(this, type, extendsTag);
+  }
+}
+
+/// A utility for changing the Dart wrapper type for elements.
+abstract class ElementUpgrader {
+  /// Upgrade the specified element to be of the Dart type this was created for.
+  ///
+  /// After upgrading the element passed in is invalid and the returned value
+  /// should be used instead.
+  Element upgrade(Element element);
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
@@ -28955,13 +28951,13 @@ class Url extends NativeFieldWrapperClass2 implements UrlUtils {
     if ((blob_OR_source_OR_stream is Blob || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_1(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is MediaSource || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is MediaStream || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_2(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is _WebKitMediaSource || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is MediaSource || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_3(blob_OR_source_OR_stream);
     }
-    if ((blob_OR_source_OR_stream is MediaStream || blob_OR_source_OR_stream == null)) {
+    if ((blob_OR_source_OR_stream is _WebKitMediaSource || blob_OR_source_OR_stream == null)) {
       return _createObjectURL_4(blob_OR_source_OR_stream);
     }
     throw new ArgumentError("Incorrect number or type of arguments");
@@ -38050,6 +38046,94 @@ class _VariableSizeListIterator<T> implements Iterator<T> {
 
   T get current => _current;
 }
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+
+/// Dartium ElementUpgrader implementation.
+class _VMElementUpgrader implements ElementUpgrader {
+  final Type _type;
+  final Type _nativeType;
+
+  _VMElementUpgrader(Document document, Type type, String extendsTag) :
+      _type = type,
+      _nativeType = _validateCustomType(type).reflectedType {
+
+    if (extendsTag == null) {
+      if (_nativeType != HtmlElement) {
+        throw new UnsupportedError('Class must provide extendsTag if base '
+              'native class is not HtmlElement');
+      }
+    } else {
+      if (document.createElement(extendsTag).runtimeType != _nativeType) {
+        throw new UnsupportedError(
+            'extendsTag does not match base native class');
+      }
+    }
+  }
+
+  Element upgrade(Element element) {
+    if (element.runtimeType != _nativeType) {
+      throw new UnsupportedError('Element is incorrect type');
+    }
+    return _Utils.changeElementWrapper(element, _type);
+    return null;
+  }
+}
+
+/// Validates that the custom type is properly formed-
+///
+/// * Is a user-defined class.
+/// * Has a created constructor with zero args.
+/// * Derives from an Element subclass.
+///
+/// Then returns the native base class.
+ClassMirror _validateCustomType(Type type) {
+  ClassMirror cls = reflectClass(type);
+  if (_isBuiltinType(cls)) {
+    throw new UnsupportedError('Invalid custom element from '
+        '${(cls.owner as LibraryMirror).uri}.');
+  }
+
+  var className = MirrorSystem.getName(cls.simpleName);
+  var createdConstructor = cls.declarations[new Symbol('$className.created')];
+  if (createdConstructor == null ||
+      createdConstructor is! MethodMirror ||
+      !createdConstructor.isConstructor) {
+    throw new UnsupportedError(
+        'Class is missing constructor $className.created');
+  }
+
+  if (createdConstructor.parameters.length > 0) {
+    throw new UnsupportedError(
+        'Constructor $className.created must take zero arguments');
+  }
+
+  Symbol objectName = reflectClass(Object).qualifiedName;
+  bool isRoot(ClassMirror cls) =>
+      cls == null || cls.qualifiedName == objectName;
+  Symbol elementName = reflectClass(HtmlElement).qualifiedName;
+  bool isElement(ClassMirror cls) =>
+      cls != null && cls.qualifiedName == elementName;
+  ClassMirror superClass = cls.superclass;
+  ClassMirror nativeClass = _isBuiltinType(superClass) ? superClass : null;
+  while(!isRoot(superClass) && !isElement(superClass)) {
+    superClass = superClass.superclass;
+    if (nativeClass == null && _isBuiltinType(superClass)) {
+      nativeClass = superClass;
+    }
+  }
+  return nativeClass;
+}
+
+
+bool _isBuiltinType(ClassMirror cls) {
+  // TODO(vsm): Find a less hackish way to do this.
+  LibraryMirror lib = cls.owner;
+  String libName = lib.uri.toString();
+  return libName.startsWith('dart:');
+}
 /**
  * A custom KeyboardEvent that attempts to eliminate cross-browser
  * inconsistencies, and also provide both keyCode and charCode information
@@ -38691,48 +38775,10 @@ class _Utils {
 
   static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;
 
-  static bool _isBuiltinType(ClassMirror cls) {
-    // TODO(vsm): Find a less hackish way to do this.
-    LibraryMirror lib = cls.owner;
-    String libName = lib.uri.toString();
-    return libName.startsWith('dart:');
-  }
-
   static void register(Document document, String tag, Type type,
       String extendsTagName) {
-    // TODO(vsm): Move these checks into native code.
-    ClassMirror cls = reflectClass(type);
-    if (_isBuiltinType(cls)) {
-      throw new UnsupportedError("Invalid custom element from ${(cls.owner as LibraryMirror).uri}.");
-    }
-    var className = MirrorSystem.getName(cls.simpleName);
-    var createdConstructor = cls.declarations[new Symbol('$className.created')];
-    if (createdConstructor == null ||
-        createdConstructor is! MethodMirror ||
-        !createdConstructor.isConstructor) {
-      throw new UnsupportedError(
-          'Class is missing constructor $className.created');
-    }
-
-    if (createdConstructor.parameters.length > 0) {
-      throw new UnsupportedError(
-          'Constructor $className.created must take zero arguments');
-    }
-
-    Symbol objectName = reflectClass(Object).qualifiedName;
-    bool isRoot(ClassMirror cls) =>
-        cls == null || cls.qualifiedName == objectName;
-    Symbol elementName = reflectClass(HtmlElement).qualifiedName;
-    bool isElement(ClassMirror cls) =>
-        cls != null && cls.qualifiedName == elementName;
-    ClassMirror superClass = cls.superclass;
-    ClassMirror nativeClass = _isBuiltinType(superClass) ? superClass : null;
-    while(!isRoot(superClass) && !isElement(superClass)) {
-      superClass = superClass.superclass;
-      if (nativeClass == null && _isBuiltinType(superClass)) {
-        nativeClass = superClass;
-      }
-    }
+    var nativeClass = _validateCustomType(type);
+
     if (extendsTagName == null) {
       if (nativeClass.reflectedType != HtmlElement) {
         throw new UnsupportedError('Class must provide extendsTag if base '
@@ -38749,6 +38795,8 @@ class _Utils {
   static Element createElement(Document document, String tagName) native "Utils_createElement";
 
   static void initializeCustomElement(HtmlElement element) native "Utils_initializeCustomElement";
+
+  static void changeElementWrapper(HtmlElement element, Type type) native "Utils_changeElementWrapper";
 }
 
 class _DOMWindowCrossFrame extends NativeFieldWrapperClass2 implements