Make AudioOutputDevice restartable and reinitializable

media/audio/audio_device_thread.h

 // 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
 #define MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 57 matching lines @@
     const int total_segments_;
     int segment_length_;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(Callback);
   };
 
   AudioDeviceThread();
   ~AudioDeviceThread();
 
-  // Starts the audio thread. The thread must not already be running.  If
+  // Starts the audio thread and suspends it. Resume() must then be called to
+  // actually start running. The thread must not already be started.  If
   // |sychronized_buffers| is set, the browser expects to be notified via the
   // |socket| every time AudioDeviceThread::Process() completes.
-  void Start(AudioDeviceThread::Callback* callback,
-             base::SyncSocket::Handle socket,
-             const char* thread_name,
-             bool synchronized_buffers);
+  void StartSuspended(const char* thread_name, bool synchronized_buffers);
 
   // This tells the audio thread to stop and clean up the data.
   // The method can stop the thread synchronously or asynchronously.
   // In the latter case, the thread will still be running after Stop()
   // returns, but the callback pointer is cleared so no further callbacks will
   // be made (IOW after Stop() returns, it is safe to delete the callback).
   // The |loop_for_join| parameter is required for asynchronous operation
   // in order to join the worker thread and close the thread handle later via a
   // posted task.
   // If set to NULL, function will wait for the thread to exit before returning.
   void Stop(base::MessageLoop* loop_for_join);
 
+  // Resumes the thread so that it starts running with the given |callback| and
+  // |socket|. This will also reset the index used for sychronized buffers.
+  void Resume(AudioDeviceThread::Callback* callback,
+              base::SyncSocket::Handle socket);
+
+  // Suspends the thread and shuts down the socket. It can be resumed again with
+  // Resume().
+  void Suspend();
+
   // Returns true if the thread is stopped or stopping.
   bool IsStopped();
 
  private:
   // Our own private SimpleThread override.  We implement this in a
   // private class so that we get the following benefits:
   // 1) AudioDeviceThread doesn't expose SimpleThread methods.
   //    I.e. the caller can't call Start()/Stop() - which would be bad.
   // 2) We override ThreadMain to add additional on-thread initialization
   //    while still synchronized with SimpleThread::Start() to provide
   //    reliable initialization.
+  // TODO(grunell): Do we still need this extra layer?
   class Thread;
 
   base::Lock thread_lock_;
   scoped_refptr<AudioDeviceThread::Thread> thread_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDeviceThread);
 };
 
 }  // namespace media.
 
 #endif  // MEDIA_AUDIO_AUDIO_DEVICE_THREAD_H_