Fixing merge issue of removal of polymer/platform.dart

pkg/polymer/test/event_handlers_test.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 polymer.test.event_handlers_test;
 
 import 'dart:async';
 import 'dart:html';
 
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
 import 'package:template_binding/template_binding.dart';
-import 'package:polymer/platform.dart' as Platform;
 
 @CustomTag('x-test')
 class XTest extends PolymerElement {
   int _testCount = 0;
   String _lastEvent;
   String _lastMessage;
   List list1 = [];
   List list2 = [];
   final _ready = new Completer();
   Future _onTestDone;
@@ skipping 82 matching lines @@
   initPolymer();
 }
 
 @initMethod _init() {
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
   test('events handled', () => (query('x-test') as XTest)._onTestDone);
 }