Fixed improper construction of custom 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 73e0a053f3af89cf3c5293e7a4d398edf9dda564..8ac51db7efaa345264307582d2494ce1e7b75fd1 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -20228,6 +20228,13 @@ class HtmlDocument extends Document {
       //
       //              See https://github.com/dart-lang/sdk/issues/23666
       int creating = 0;
+
+      // If any JS code is hooked we want to call it too.
+      var oldCreatedCallback = elemProto['createdCallback'];
+      var oldAttributeChangedCallback = elemProto['attributeChangedCallback'];
+      var oldAttachedCallback = elemProto['attachedCallback'];
+      var oldDetachedCallback = elemProto['detachedCallback'];
+
       // TODO(jacobr): warning:
       elemProto['createdCallback'] = js.JsNative.withThis(($this) {
         if (_getJSClassName(reflectClass(customElementClass).superclass) != null && creating < 2) {
@@ -20266,15 +20273,27 @@ class HtmlDocument extends Document {
             creating--;
           }
         }
+
+        if (oldCreatedCallback != null)
+          oldCreatedCallback.apply([], thisArg: unwrap_jso($this));
       });
       elemProto['attributeChangedCallback'] = new js.JsFunction.withThis(($this, attrName, oldVal, newVal) {
         $this.attributeChanged(attrName, oldVal, newVal);
+
+        if (oldAttributeChangedCallback != null)
+          oldAttributeChangedCallback.apply([], thisArg: unwrap_jso($this));
       });
       elemProto['attachedCallback'] = new js.JsFunction.withThis(($this) {
         $this.attached();
+
+        if (oldAttachedCallback != null)
+          oldAttachedCallback.apply([], thisArg: unwrap_jso($this));
       });
       elemProto['detachedCallback'] = new js.JsFunction.withThis(($this) {
         $this.detached();
+
+        if (oldDetachedCallback != null)
+          oldDetachedCallback.apply([], thisArg: unwrap_jso($this));
       });
       // document.registerElement('x-foo', {prototype: elemProto, extends: extendsTag});
       var jsMap = new js.JsObject.jsify({'prototype': elemProto, 'extends': extendsTag});
@@ -36962,10 +36981,10 @@ class Url extends DartHtmlDomObject implements UrlUtils {
     if ((blob_OR_source_OR_stream is Blob || blob_OR_source_OR_stream == null)) {
       return _blink.BlinkURL.instance.createObjectURL_Callback_1_(unwrap_jso(blob_OR_source_OR_stream));
     }
-    if ((blob_OR_source_OR_stream is MediaSource)) {
+    if ((blob_OR_source_OR_stream is MediaStream)) {
       return _blink.BlinkURL.instance.createObjectURL_Callback_1_(unwrap_jso(blob_OR_source_OR_stream));
     }
-    if ((blob_OR_source_OR_stream is MediaStream)) {
+    if ((blob_OR_source_OR_stream is MediaSource)) {
       return _blink.BlinkURL.instance.createObjectURL_Callback_1_(unwrap_jso(blob_OR_source_OR_stream));
     }
     throw new ArgumentError("Incorrect number or type of arguments");