Add an optional argument to HTMLCanvasElement.toDataURL.

lib/dom/dom.dart

 #library('dart:dom_deprecated');
 
 // 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.
 
 // DO NOT EDIT
 // Auto-generated Dart DOM library with no implementation.
 
 
@@ skipping 3451 matching lines @@
 // WARNING: Do not edit - generated code.
 
 interface HTMLCanvasElement extends HTMLElement {
 
   int height;
 
   int width;
 
   Object getContext(String contextId);
 
-  String toDataURL(String type);
+  String toDataURL(String type, [num quality]);
 }
 // 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.
 
 // WARNING: Do not edit - generated code.
 
 interface HTMLCollection extends List<Node> {
 
   final int length;
@@ skipping 9601 matching lines @@
 // 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.
 
 Window get window() => _dummy();
 
 // TODO(vsm): Remove when prefixes are supported.
 Window get dom_window() => _dummy();
 
 Document get document() => _dummy();