Use @Native annotation on dart2js DOM native classes

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

 // Copyright (c) 2013, 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 {
+$(ANNOTATIONS)$(NATIVESPEC)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 $!MEMBERS
 
   /**
    * Sets the currently bound texture to [data].
    *
    * [data] can be either an [ImageElement], a
    * [CanvasElement], a [VideoElement], or an [ImageData] object.
    *
    * To use [texImage2d] with a TypedData object, use [texImage2dTyped].
    *
@@ skipping 68 matching lines @@
       int type, TypedData data) native;
 $else
   void texSubImage2DTyped(int targetTexture, int levelOfDetail,
       int xOffset, int yOffset, int width, int height, int format,
       int type, TypedData data) {
     texSubImage2D(targetTexture, levelOfDetail, xOffset, yOffset,
         width, height, format, type, data);
   }
 $endif
 }