Get rid of ===/!===.

lib/html/src/dart2js_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.
 
 // TODO(vsm): Unify with Dartium version.
 class _DOMWindowCrossFrameImpl implements Window {
   // Private window.  Note, this is a window in another frame, so it
   // cannot be typed as "Window" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
   var _window;
@@ skipping 28 matching lines @@
       JS('void', '#.postMessage(#,#)', _window, message, targetOrigin);
     } else {
       JS('void', '#.postMessage(#,#,#)', _window, message, targetOrigin, messagePorts);
     }
   }
 
   // Implementation support.
   _DOMWindowCrossFrameImpl(this._window);
 
   static Window _createSafe(w) {
-    if (w === window) {
+    if (identical(w, window)) {
       return w;
     } else {
       // TODO(vsm): Cache or implement equality.
       return new _DOMWindowCrossFrameImpl(w);
     }
   }
 }
 
 class _LocationCrossFrameImpl implements Location {
   // Private location.  Note, this is a location object in another frame, so it
   // cannot be typed as "Location" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
   var _location;
 
   void set href(String val) => _setHref(_location, val);
   static void _setHref(location, val) {
     JS('void', '#.href = #', location, val);
   }
 
   // Implementation support.
   _LocationCrossFrameImpl(this._location);
 
   static Location _createSafe(location) {
-    if (location === window.location) {
+    if (identical(location, window.location)) {
       return location;
     } else {
       // TODO(vsm): Cache or implement equality.
       return new _LocationCrossFrameImpl(location);
     }
   }
 }
 
 class _HistoryCrossFrameImpl implements History {
   // Private history.  Note, this is a history object in another frame, so it
   // cannot be typed as "History" as its prototype is not patched
   // properly.  Its fields and methods can only be accessed via JavaScript.
   var _history;
 
   void back() => JS('void', '#.back()', _history);
 
   void forward() => JS('void', '#.forward()', _history);
 
   void go(int distance) => JS('void', '#.go(#)', _history, distance);
 
   // Implementation support.
   _HistoryCrossFrameImpl(this._history);
 
   static History _createSafe(h) {
-    if (h === window.history) {
+    if (identical(h, window.history)) {
       return h;
     } else {
       // TODO(vsm): Cache or implement equality.
       return new _HistoryCrossFrameImpl(h);
     }
   }
 }