Minimal fix to get cross frame tests working, take #2.

lib/dom/templates/html/frog/impl_IFrameElement.darttemplate

Index: lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
diff --git a/lib/dom/templates/html/dartium/impl_Window.darttemplate b/lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
similarity index 51%
copy from lib/dom/templates/html/dartium/impl_Window.darttemplate
copy to lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
index 0713050ab288c22451da77bfbd0059874961dfc3..204154d30fae31d09d13016b5d7e8f8b819afee4 100644
--- a/lib/dom/templates/html/dartium/impl_Window.darttemplate
+++ b/lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
@@ -3,15 +3,12 @@
 // BSD-style license that can be found in the LICENSE file.
 
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$!MEMBERS
 
-  _DocumentImpl get document() => _wrap(_ptr.document);
+  Window get _contentWindow() native "return this.contentWindow;";
 
-  void requestLayoutFrame(TimeoutHandler callback) {
-    _addMeasurementFrameCallback(callback);
+  // Override contentWindow to return secure wrapper.
+  Window get contentWindow() {
+    return _DOMWindowCrossFrameImpl._createSafe(_contentWindow);
   }
-
-  int requestAnimationFrame(RequestAnimationFrameCallback callback) =>
-      webkitRequestAnimationFrame(callback);
-
-$!MEMBERS
 }