Fixed native element extension, custom events, _VMUpgrader, and data binding.

tools/dom/src/dartium_CustomElementSupport.dart

Index: tools/dom/src/dartium_CustomElementSupport.dart
diff --git a/tools/dom/src/dartium_CustomElementSupport.dart b/tools/dom/src/dartium_CustomElementSupport.dart
index 85ff4d6aca78a57460bc5bff8ee08d3dd4ab552c..c91ab72034051200832e2bb5ca8e29b0265eb8ce 100644
--- a/tools/dom/src/dartium_CustomElementSupport.dart
+++ b/tools/dom/src/dartium_CustomElementSupport.dart
@@ -8,9 +8,11 @@ part of dart.dom.html;
 class _VMElementUpgrader implements ElementUpgrader {
   final Type _type;
   final Type _nativeType;
+  final String _extendsTag;
 
   _VMElementUpgrader(Document document, Type type, String extendsTag) :
       _type = type,
+      _extendsTag = extendsTag,
       _nativeType = _validateCustomType(type).reflectedType {
 
     if (extendsTag == null) {
@@ -28,20 +30,39 @@ class _VMElementUpgrader implements ElementUpgrader {
 
   Element upgrade(element) {
     var jsObject;
-    var tag = _getCustomElementName(element);
+    var tag;
+    var isNativeElementExtension = false;
+
+    try {
+      tag = _getCustomElementName(element);
+    } catch (e) {
+      isNativeElementExtension = element.localName == _extendsTag;
+    }
+
     if (element.runtimeType == HtmlElement || element.runtimeType == TemplateElement) {
+      if (tag != _extendsTag) {
+        throw new UnsupportedError('$tag is not registered.');
+      }
       jsObject = unwrap_jso(element);
     } else if (element.runtimeType == js.JsObjectImpl) {
       // It's a Polymer core element (written in JS).
       jsObject = element;
-    } else {
+    } else if (isNativeElementExtension) {
+      // Extending a native element.
+      jsObject = element.blink_jsObject;
+
+      // Element to extend is the real tag.
+      tag = element.localName;
+    } else if (tag != null && element.localName != tag) { 
+      throw new UnsupportedError('Element is incorrect type. Got ${element.runtimeType}, expected native Html or Svg element to extend.');
+    } else if (tag == null) {
       throw new UnsupportedError('Element is incorrect type. Got ${element.runtimeType}, expected HtmlElement/JsObjectImpl.');
     }
 
     // Remember Dart class to tagName for any upgrading done in wrap_jso.
-    _addCustomElementType(tag, _type);
+    _addCustomElementType(tag, _type, _extendsTag);
 
-    return createCustomUpgrader(_nativeType, jsObject);
+    return createCustomUpgrader(_type, jsObject);
   }
 }