Remove vestigial constructors in Frog implementation classes.

client/dom/src/_FactoryProviders.dart

Index: client/dom/src/_FactoryProviders.dart
diff --git a/client/dom/src/_FactoryProviders.dart b/client/dom/src/_FactoryProviders.dart
index 56491d0d527435137920ad9fe50c3c1e557ecd75..938d1bfe1a2d13bf91235515d2d275c24b50854f 100644
--- a/client/dom/src/_FactoryProviders.dart
+++ b/client/dom/src/_FactoryProviders.dart
@@ -1,11 +1,7 @@
-// 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(); }