Use @Native annotation on dart2js DOM native classes

tools/dom/templates/html/impl/impl_HTMLCanvasElement.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_MODIFIERS)class $CLASSNAME$EXTENDS implements CanvasImageSource$IMPLEMENTS$NATIVESPEC {
+$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS implements CanvasImageSource$IMPLEMENTS {
 $!MEMBERS
   /** An API for drawing on this canvas. */
 $if DART2JS
   CanvasRenderingContext2D get context2D =>
       JS('Null|CanvasRenderingContext2D', '#.getContext(#)', this, '2d');
 $else
   CanvasRenderingContext2D get context2D => getContext('2d');
 $endif
 
   /**
@@ skipping 64 matching lines @@
    *
    * * [Data URI Scheme](http://en.wikipedia.org/wiki/Data_URI_scheme) from Wikipedia.
    *
    * * [HTMLCanvasElement](https://developer.mozilla.org/en-US/docs/DOM/HTMLCanvasElement) from MDN.
    *
    * * [toDataUrl](http://dev.w3.org/html5/spec/the-canvas-element.html#dom-canvas-todataurl) from W3C.
    */
   String toDataUrl([String type = 'image/png', num quality]) =>
       _toDataUrl(type, quality);
 }