Remove usage of dart:json.

tools/dom/templates/html/dartium/html_dartium.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.
 
 // DO NOT EDIT
 // Auto-generated dart:html library.
 
 /// The Dart HTML library.
 ///
 /// For examples, see
 /// [Dart HTML5 Samples](https://github.com/dart-lang/dart-html5-samples)
 /// on Github.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol, deprecated;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
-import 'dart:json' as json;
+import "dart:convert";
 import 'dart:math';
 // TODO(vsm): Remove this when we can do the proper checking in
 // native code for custom elements.
 import 'dart:mirrors';
 import 'dart:nativewrappers';
 import 'dart:typed_data';
 import 'dart:web_gl' as gl;
 import 'dart:web_sql';
 // Not actually used, but imported since dart:html can generate these objects.
 import 'dart:svg' as svg;
@@ skipping 74 matching lines @@
 ElementList queryAll(String selector) => document.queryAll(selector);
 
 int _getNewIsolateId() => _Utils._getNewIsolateId();
 
 bool _callPortInitialized = false;
 var _callPortLastResult = null;
 
 _callPortSync(num id, var message) {
   if (!_callPortInitialized) {
     window.on['js-result'].listen((event) {
-      _callPortLastResult = json.parse(_getPortSyncEventData(event));
+      _callPortLastResult = JSON.decode(_getPortSyncEventData(event));
     });
     _callPortInitialized = true;
   }
   assert(_callPortLastResult == null);
   _dispatchEvent('js-sync-message', {'id': id, 'message': message});
   var result = _callPortLastResult;
   _callPortLastResult = null;
   return result;
 }