Optimize dartium dart:html bindings so real world application performance is acceptable. Improves d…

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 e769e888882d95f9fd1295fa7bef63373d936144..4bccce15408d0702dbcd5636d48ec9a88ae1bc44 100644
--- a/tools/dom/src/dartium_CustomElementSupport.dart
+++ b/tools/dom/src/dartium_CustomElementSupport.dart
@@ -29,7 +29,6 @@ class _VMElementUpgrader implements ElementUpgrader {
   }
 
   Element upgrade(element) {
-    var jsObject;
     var tag;
     var isNativeElementExtension = false;
 
@@ -43,13 +42,11 @@ class _VMElementUpgrader implements ElementUpgrader {
       if (tag != _extendsTag) {
         throw new UnsupportedError('$tag is not registered.');
       }
-      jsObject = unwrap_jso(element);
     } else if (element.runtimeType == js.JsObject) {
       // It's a Polymer core element (written in JS).
-      jsObject = element;
     } else if (isNativeElementExtension) {
       // Extending a native element.
-      jsObject = element.blink_jsObject;
+      // TODO(jacobr): make sure we haven't busted this case.
 
       // Element to extend is the real tag.
       tag = element.localName;
@@ -59,10 +56,11 @@ class _VMElementUpgrader implements ElementUpgrader {
       throw new UnsupportedError('Element is incorrect type. Got ${element.runtimeType}, expected HtmlElement/JsObject.');
     }
 
-    // Remember Dart class to tagName for any upgrading done in wrap_jso.
+    // Remember Dart class to tagName for any upgrading
     addCustomElementType(tag, _type, _extendsTag);
 
-    return _createCustomUpgrader(_type, jsObject);
+    // TODO(jacobr): XXX validate that this method still works.
+    return _createCustomUpgrader(_type, element);
   }
 }