Fix dataTransfer getter

BUG=

Review-Url: https://codereview.chromium.org/2907273003 .
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 008c374..34c3446 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -28998,7 +28998,7 @@
 
   @DomName('MouseEvent.dataTransfer')
   DataTransfer get dataTransfer =>
-      js.JsNative.getProperty(js.context, 'dataTransfer');
+      js.JsNative.getProperty(this, 'dataTransfer');
 }
 // 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
@@ -41281,11 +41281,11 @@
       return _blink.BlinkURL.instance
           .createObjectURL_Callback_1_(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_(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_(blob_OR_source_OR_stream);
     }
diff --git a/tools/dom/templates/html/dartium/impl_MouseEvent.darttemplate b/tools/dom/templates/html/dartium/impl_MouseEvent.darttemplate
index cc263cf..a091220 100644
--- a/tools/dom/templates/html/dartium/impl_MouseEvent.darttemplate
+++ b/tools/dom/templates/html/dartium/impl_MouseEvent.darttemplate
@@ -74,6 +74,6 @@
   Point get page => new Point/*<num>*/(_pageX, _pageY);
 
   @DomName('MouseEvent.dataTransfer')
-  DataTransfer get dataTransfer => js.JsNative.getProperty(js.context, 'dataTransfer');
+  DataTransfer get dataTransfer => js.JsNative.getProperty(this, 'dataTransfer');
 
 }