Revert "Minimal fix to get cross frame tests working."

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

Index: lib/dom/templates/html/frog/impl_Window.darttemplate
diff --git a/lib/dom/templates/html/frog/impl_Window.darttemplate b/lib/dom/templates/html/frog/impl_Window.darttemplate
index 78335ee8d057cfc33755ccefcb7eb6afed36cd74..746e5921b9942d51f2d7496ff72eae38229d65ad 100644
--- a/lib/dom/templates/html/frog/impl_Window.darttemplate
+++ b/lib/dom/templates/html/frog/impl_Window.darttemplate
@@ -6,11 +6,6 @@ class $CLASSNAME$EXTENDS$IMPLEMENTS native "@*DOMWindow" {
 
   _DocumentImpl get document() native "return this.document;";
 
-  Window get _top() native "return this.top;";
-
-  // Override top to return secure wrapper.
-  Window get top() => _DOMWindowCrossFrameImpl._createSafe(_top);
-
   void requestLayoutFrame(TimeoutHandler callback) {
     _addMeasurementFrameCallback(callback);
   }