Safely wrap window.top in frog dom.

client/dom/src/frog_DOMImplementation.dart

 // 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
 // BSD-style license that can be found in the LICENSE file.
 
-class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
-$!MEMBERS
-
-  Window get _contentWindow() native "return this.contentWindow;";
-
-  // Override contentWindow to return secure wrapper.
-  Window get contentWindow() {
-    return _DOMWindowCrossFrameImpl._createSafe(_contentWindow);
-  }
-}
-
 // TODO(vsm): Unify with Dartium version.
 class _DOMWindowCrossFrameImpl implements DOMType, DOMWindow {
   // Private window.
   _DOMWindowJs _window;
 
   // DOMType
   var dartObjectLocalStorage;
   String get typeName() => "DOMWindow";
 
   // Fields.
-  // TODO(vsm): Wrap these two.
-  History get history() => _window.history;
-  Location get location() => _window.location;
+  // TODO(vsm): Implement history and location getters.
 
   bool get closed() => _window.closed;
   int get length() => _window.length;
-  DOMWindow get opener() => _createDOMWindowCrossFrame(_window.opener);
-  DOMWindow get parent() => _createDOMWindowCrossFrame(_window.parent);
-  DOMWindow get top() => _createDOMWindowCrossFrame(_window.top);
+  DOMWindow get opener() => _createSafe(_window.opener);
+  DOMWindow get parent() => _createSafe(_window.parent);
+  DOMWindow get top() => _createSafe(_window.top);
 
   // Methods.
-  void focus() {
-    _window.focus();
-  }
+  void focus() => _window.focus();
 
-  void blur() {
-    _window.blur();
-  }
+  void blur() => _window.blur();
 
-  void close() {
-    _window.close();
-  }
+  void close() => _window.close();
 
   void postMessage(Dynamic message,
                    String targetOrigin,
                    [List messagePorts = null]) {
     if (messagePorts == null) {
       _window.postMessage(message, targetOrigin);
     } else {
       _window.postMessage(message, targetOrigin, messagePorts);
     }
   }
 
   // Implementation support.
   _DOMWindowCrossFrameImpl(this._window);
 
   static DOMWindow _createSafe(w) {
-    // TODO(vsm): Check if it's the top-level window.  Return unwrapped.
-
-    // TODO(vsm): Cache or implement equality.
-    return new _DOMWindowCrossFrameImpl(w);
+    if (w === window) {
+      return w;
+    } else {
+      // TODO(vsm): Cache or implement equality.
+      return new _DOMWindowCrossFrameImpl(w);
+    }
   }
 }