Extract LazyBackgroundTaskQueue from ExtensionSystem.

chrome/browser/extensions/api/messaging/message_service.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/messaging/message_service.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/json/json_writer.h"
@@ skipping 200 matching lines @@
   DCHECK_EQ(GET_CHANNEL_ID(port1_id), channel_id);
   DCHECK_EQ(GET_CHANNEL_OPENER_ID(channel_id), port1_id);
   DCHECK_EQ(GET_CHANNEL_RECEIVERS_ID(channel_id), port2_id);
 
   *port1 = port1_id;
   *port2 = port2_id;
 }
 
 MessageService::MessageService(BrowserContext* context)
     : lazy_background_task_queue_(
-          ExtensionSystem::Get(context)->lazy_background_task_queue()),
+          LazyBackgroundTaskQueue::Get(context)),
       weak_factory_(this) {
   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
                  content::NotificationService::AllBrowserContextsAndSources());
   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
                  content::NotificationService::AllBrowserContextsAndSources());
 }
 
 MessageService::~MessageService() {
   STLDeleteContainerPairSecondPointers(channels_.begin(), channels_.end());
   channels_.clear();
@@ skipping 678 matching lines @@
                                              int channel_id) {
   MessageChannelMap::iterator channel_iter = channels_.find(channel_id);
   if (channel_iter != channels_.end()) {
     for (const PendingMessage& message : queue) {
       DispatchMessage(message.first, channel_iter->second, message.second);
     }
   }
 }
 
 }  // namespace extensions