Remove vestigial constructors in Frog implementation classes.

client/dom/src/_FactoryProviders.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
-
-// These factory methods could all live in one factory provider class but dartc
-// has a bug (5399939) preventing that.
-
 class _AudioContextFactoryProvider {
 
   factory AudioContext() { return create(); }
 
   static AudioContext create() native;
 }
 
 class _DOMParserFactoryProvider {
 
   factory DOMParser() { return create(); }
@@ skipping 79 matching lines @@
 
   static WebKitPoint create(url) native;
 }
 
 class _XMLHttpRequestFactoryProvider {
 
   factory XMLHttpRequest() { return create(); }
 
   static XMLHttpRequest create() native;
 }