Fixing broken tests because of mismatch of suppressed warnings.

tools/dom/templates/html/impl/impl_WheelEvent.darttemplate

 // 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 $LIBRARYNAME;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   factory WheelEvent(String type,
       {Window view, int deltaX: 0, int deltaY: 0,
@@ skipping 32 matching lines @@
       if (metaKey) {
         modifiers.push('Meta');
       }
       event._initWheelEvent(type, canBubble, cancelable, view, detail, screenX,
           screenY, clientX, clientY, button, relatedTarget, modifiers.join(' '),
           deltaX, deltaY, 0, 0);
     } else if (event._hasInitMouseScrollEvent) {
       var axis = 0;
       var detail = 0;
       if (deltaX != 0 && deltaY != 0) {
-        throw UnsupportedError(
+        throw new UnsupportedError(
             'Cannot modify deltaX and deltaY simultaneously');
       }
       if (deltaY != 0) {
         detail = deltaY;
         axis = JS('int', 'MouseScrollEvent.VERTICAL_AXIS');
       } else if (deltaX != 0) {
         detail = deltaX;
         axis = JS('int', 'MouseScrollEvent.HORIZONTAL_AXIS');
       }
       event._initMouseScrollEvent(type, canBubble, cancelable, view, detail,
@@ skipping 173 matching lines @@
    * [deltaMode].
    *
    * See also:
    *
    * * [WheelEvent.deltaY](http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-WheelEvent-deltaY) from the W3C.
    */
   @DomName('WheelEvent.deltaY')
   num get deltaY => -_wheelDeltaY;
 $endif
 }