Fixing up DOM constructors.

tools/dom/templates/html/impl/impl_CanvasRenderingContext2D.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 {
+$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 $!MEMBERS
 
   /**
    * Sets the color used inside shapes.
    * [r], [g], [b] are 0-255, [a] is 0-1.
    */
   void setFillColorRgb(int r, int g, int b, [num a = 1]) {
     this.fillStyle = 'rgba($r, $g, $b, $a)';
   }
 
@@ skipping 242 matching lines @@
   @DomName('CanvasRenderingContext2D.lineDashOffset')
   void set lineDashOffset(num value) => JS('void',
       'typeof #.lineDashOffset != "undefined" ? #.lineDashOffset = # : '
       '#.webkitLineDashOffset = #', this, this, value, this, value);
 $else
   // TODO(amouravski): Add Dartium native methods for drawImage once we figure
   // out how to not break native bindings.
 $endif
 }