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

media/audio/linux/alsa_output_unittest.cc

 // 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.
 
 #include "base/message_loop.h"
 #include "base/stringprintf.h"
 #include "media/audio/linux/alsa_output.h"
 #include "media/audio/linux/alsa_wrapper.h"
 #include "media/audio/linux/audio_manager_linux.h"
 #include "media/base/data_buffer.h"
@@ skipping 70 matching lines @@
   MOCK_METHOD1(MakeAudioOutputStream, AudioOutputStream*(
       const AudioParameters& params));
   MOCK_METHOD2(MakeAudioInputStream, AudioInputStream*(
       const AudioParameters& params, const std::string& device_id));
   MOCK_METHOD0(MuteAll, void());
   MOCK_METHOD0(UnMuteAll, void());
   MOCK_METHOD1(ReleaseOutputStream, void(AudioOutputStream* stream));
 
   // We don't mock this method since all tests will do the same thing
   // and use the current message loop.
-  virtual MessageLoop* GetMessageLoop() {
-    return MessageLoop::current();
+  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() OVERRIDE {
+    return MessageLoop::current()->message_loop_proxy();
   }
 };
 
 class AlsaPcmOutputStreamTest : public testing::Test {
  protected:
   AlsaPcmOutputStreamTest() {
     mock_manager_ = new StrictMock<MockAudioManagerLinux>();
     test_stream_.reset(CreateStream(kTestChannelLayout));
   }
 
@@ skipping 680 matching lines @@
 
   test_stream_->stop_stream_ = true;
   test_stream_->ScheduleNextWrite(true);
 
   // TODO(ajwong): Find a way to test whether or not another task has been
   // posted so we can verify that the Alsa code will indeed break the task
   // posting loop.
 
   test_stream_->TransitionTo(AlsaPcmOutputStream::kIsClosed);
 }