Make fill parameter in context2d default to 'nonzero' as per the spec.

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_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 $!MEMBERS
 
   /**
@@ skipping 324 matching lines @@
    * drawn text.
    */
   @DomName('CanvasRenderingContext2D.fillText')
   void fillText(String text, num x, num y, [num maxWidth]) {
     if (maxWidth != null) {
       JS('void', '#.fillText(#, #, #, #)', this, text, x, y, maxWidth);
     } else {
       JS('void', '#.fillText(#, #, #)', this, text, x, y);
     }
   }
+
+  @DomName('CanvasRenderingContext2D.fill')
+  void fill([String winding = 'nonzero']) {
+    JS('void', '#.fill(#)', this, winding);
+  }
 $endif
 }