Remove usage of dart:json.

tests/html/dromaeo_noop/dromaeo_smoke.dart

 // Copyright (c) 2013, 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.
 
 library dromaeo;
 import 'dart:async';
 import 'dart:html';
-import 'dart:json' as json;
+import "dart:convert";
 import '../../../samples/third_party/dromaeo/common/common.dart';
 import 'dart:math' as Math;
 import '../../../pkg/unittest/lib/unittest.dart';
 import '../../../pkg/unittest/lib/html_config.dart';
 part '../../../samples/third_party/dromaeo/tests/Common.dart';
 part '../../../samples/third_party/dromaeo/tests/RunnerSuite.dart';
 
 /**
  * The smoketest equivalent of an individual test run, much like
  * dom-attr-html.dart, dom-modify-html.dart, dom-query-html.dart and others.
  */
 void main() {
   new Suite(window, 'dom-nothing')
     .prep(() {})
     .test('no-op', () {})
     .end();
 }