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 95c43f64b33d9239ec51225fad5095bae41037c2..a3885eeec5d4a4e09e1631e69b17e27724cf4f17 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -1145,10 +1145,19 @@ unwrap_jso(dartClass_instance) {
  */
 wrap_jso(jsObject) {
   try {
-    if (jsObject is! js.JsObject) {
+    if (jsObject is! js.JsObject || jsObject == null) {
       // JS Interop converted the object to a Dart class e.g., Uint8ClampedList.
+      // or it's a simple type.
       return jsObject;
     }
+
+    // TODO(alanknight): With upgraded custom elements this causes a failure because
+    // we need a new wrapper after the type changes. We could possibly invalidate this
+    // if the constructor name didn't match?
+    if (jsObject.dartWrapper != null) {
+      return jsObject.dartWrapper;

[Jacob, 2015/10/01 21:07:47]

change this to _dartWrapper and add a helper method with a unique name in
dart:js that gets it.

+    }
+
     // Try the most general type conversions on it.
     // TODO(alanknight): We may be able to do better. This maintains identity,
     // which is useful, but expensive. And if we nest something that only
@@ -1175,6 +1184,7 @@ wrap_jso(jsObject) {
       if (func != null) {
         dartClass_instance = func();
         dartClass_instance.blink_jsObject = jsObject;
+        jsObject.dartWrapper = dartClass_instance;
       }
     }
     return dartClass_instance;
@@ -37168,10 +37178,10 @@ class Url extends NativeFieldWrapperClass2 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 MediaStream)) {
+    if ((blob_OR_source_OR_stream is MediaSource)) {
       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));
     }
     throw new ArgumentError("Incorrect number or type of arguments");