Adding 'part of html' to all files which are used by dart:html.

sdk/lib/html/src/Isolates.dart

Index: sdk/lib/html/src/Isolates.dart
diff --git a/sdk/lib/html/src/Isolates.dart b/sdk/lib/html/src/Isolates.dart
index 7fc027721e9ceaf24eecf46f227d0795cc8a7e24..fe0ea4b0373a53cbb8e927d0c7fc892b8bad02b2 100644
--- a/sdk/lib/html/src/Isolates.dart
+++ b/sdk/lib/html/src/Isolates.dart
@@ -2,6 +2,8 @@
 // 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 html;
+
 _serialize(var message) {
   return new _JsSerializer().traverse(message);
 }