Add thread safety to AudioManagerBase to protect access to the audio thread member variable.

content/test/webrtc_audio_device_test.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_TEST_WEBRTC_AUDIO_DEVICE_TEST_H_
 #define CONTENT_TEST_WEBRTC_AUDIO_DEVICE_TEST_H_
 #pragma once
 
 #include <string>
 
@@ skipping 126 matching lines @@
 
   void OnGetHardwareSampleRate(double* sample_rate);
   void OnGetHardwareInputSampleRate(double* sample_rate);
 
   // IPC::Channel::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
   // Posts a final task to the IO message loop and waits for completion.
   void WaitForIOThreadCompletion();
   void WaitForAudioManagerCompletion();
-  void WaitForMessageLoopCompletion(MessageLoop* loop);
+  void WaitForMessageLoopCompletion(base::MessageLoopProxy* loop);
 
   // Convenience getter for gmock.
   MockMediaObserver& media_observer() const {
     return *media_observer_.get();
   }
 
   std::string GetTestDataPath(const FilePath::StringType& file_name);
 
   scoped_ptr<ReplaceContentClientRenderer> saved_content_renderer_;
   MessageLoopForUI message_loop_;
@@ skipping 28 matching lines @@
   virtual ~WebRTCTransportImpl();
 
   virtual int SendPacket(int channel, const void* data, int len) OVERRIDE;
   virtual int SendRTCPPacket(int channel, const void* data, int len) OVERRIDE;
 
  private:
   webrtc::VoENetwork* network_;
 };
 
 #endif  // CONTENT_TEST_WEBRTC_AUDIO_DEVICE_TEST_H_