Revert "Dartium JS Interop enabled."

tools/dom/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.
 
 part of html;
 
 // TODO(vsm): Unify with Dartium version.
 class _DOMWindowCrossFrame implements WindowBase {
   // Private window.  Note, this is a window in another frame, so it
   // cannot be typed as "Window" as its prototype is not patched
@@ skipping 65 matching lines @@
       [bool useCapture]) => throw new UnsupportedError(
           'You can only attach EventListeners to your own window.');
 }
 
 class _LocationCrossFrame implements LocationBase {
   // 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;
 
-  set href(String val) => _setHref(_location, val);
+  void set href(String val) => _setHref(_location, val);
   static void _setHref(location, val) {
     JS('void', '#.href = #', location, val);
   }
 
   // Implementation support.
   _LocationCrossFrame(this._location);
 
   static LocationBase _createSafe(location) {
     if (identical(location, window.location)) {
       return location;
@@ skipping 21 matching lines @@
 
   static HistoryBase _createSafe(h) {
     if (identical(h, window.history)) {
       return h;
     } else {
       // TODO(vsm): Cache or implement equality.
       return new _HistoryCrossFrame(h);
     }
   }
 }