Fix a memory leak in browser tests.

lib/src/runner/browser/browser_manager.dart

 // Copyright (c) 2015, 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 test.runner.browser.browser_manager;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:async/async.dart';
@@ skipping 176 matching lines @@
       _channel.sink.add({
         "command": "closeSuite",
         "id": suiteId
       });
     }
 
     var response = await _pool.withResource(() {
       _channel.sink.add({
         "command": "loadSuite",
         "url": url.toString(),
-        "id": _suiteId++,
+        "id": suiteId,
         "channel": suiteVirtualChannel.id
       });
 
       // Create a nested MultiChannel because the iframe will be using a channel
       // wrapped within the host's channel.
       suiteChannel = new MultiChannel(
           suiteVirtualChannel.stream, suiteVirtualChannel.sink);
 
       var completer = new Completer();
       suiteChannel.stream.listen((response) {
@@ skipping 83 matching lines @@
 
   final Uri observatoryUrl;
 
   final Uri remoteDebuggerUrl;
 
   _BrowserEnvironment(this._manager, this.observatoryUrl,
       this.remoteDebuggerUrl);
 
   CancelableFuture displayPause() => _manager._displayPause();
 }