Make AudioOutputDevice restartable and reinitializable

media/audio/audio_output_device.h

Index: media/audio/audio_output_device.h
diff --git a/media/audio/audio_output_device.h b/media/audio/audio_output_device.h
index c0faacd11517fab6c80e168a0c433b627dfb5561..4d49fd0a654c694f149f9118af69741cd3437f7d 100644
--- a/media/audio/audio_output_device.h
+++ b/media/audio/audio_output_device.h
@@ -45,8 +45,8 @@
 // 1. Creating thread.
 //    Must be the main render thread.
 // 2. Control thread (may be the main render thread or another thread).
-//    The methods: Start(), Stop(), Play(), Pause(), SetVolume()
-//    must be called on the same thread.
+//    The methods Initialize(), Start(), and Stop() must be called on the same
+//    thread.
 // 3. IO thread (internal implementation detail - not exposed to public API)
 //    The thread within which this class receives all the IPC messages and
 //    IPC communications can only happen in this thread.
@@ -56,8 +56,7 @@
 //    the audio layer in the browser process using sync sockets and shared
 //    memory.
 //
-// Implementation notes:
-// - The user must call Stop() before deleting the class instance.
+// NOTE: The user must call Stop() before deleting the class instance.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_
@@ -69,6 +68,7 @@
 #include "base/macros.h"
 #include "base/memory/shared_memory.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/threading/thread_checker.h"
 #include "media/audio/audio_device_thread.h"
 #include "media/audio/audio_output_ipc.h"
 #include "media/audio/scoped_task_runner_observer.h"
@@ -84,7 +84,7 @@ class OneShotTimer;
 namespace media {
 
 class MEDIA_EXPORT AudioOutputDevice
-    : NON_EXPORTED_BASE(public AudioRendererSink),
+    : NON_EXPORTED_BASE(public RestartableAudioRendererSink),
       NON_EXPORTED_BASE(public AudioOutputIPCDelegate),
       NON_EXPORTED_BASE(public ScopedTaskRunnerObserver) {
  public:
@@ -102,7 +102,7 @@ class MEDIA_EXPORT AudioOutputDevice
 
   // AudioRendererSink implementation.
   void Initialize(const AudioParameters& params,
-                  RenderCallback* callback) override;
+                  AudioRendererSink::RenderCallback* callback) override;
   void Start() override;
   void Stop() override;
   void Play() override;
@@ -144,10 +144,10 @@ class MEDIA_EXPORT AudioOutputDevice
   // be executed on that thread.  They use AudioOutputIPC to send IPC messages
   // upon state changes.
   void RequestDeviceAuthorizationOnIOThread();
-  void CreateStreamOnIOThread(const AudioParameters& params);
+  void CreateStreamOnIOThread();
   void PlayOnIOThread();
   void PauseOnIOThread();
-  void ShutDownOnIOThread();
+  void StopOnIOThread();
   void SetVolumeOnIOThread(double volume);
 
   // Process device authorization result on the IO thread.
@@ -161,9 +161,10 @@ class MEDIA_EXPORT AudioOutputDevice
   // If the IO loop dies before we do, we shut down the audio thread from here.
   void WillDestroyCurrentMessageLoop() override;
 
-  AudioParameters audio_parameters_;
+  // Reports error to |render_callback_|.
+  void ReportRenderError();
 
-  RenderCallback* callback_;
+  AudioParameters audio_parameters_;
 
   // A pointer to the IPC layer that takes care of sending requests over to
   // the AudioRendererHost.  Only valid when state_ != IPC_CLOSED and must only
@@ -195,11 +196,17 @@ class MEDIA_EXPORT AudioOutputDevice
   // Our audio thread callback class.  See source file for details.
   class AudioThreadCallback;
 
-  // In order to avoid a race between OnStreamCreated and Stop(), we use this
-  // guard to control stopping and starting the audio thread.
-  base::Lock audio_thread_lock_;
+  // This lock is used in order to:
+  // (1) Avoid a race between OnStreamCreated() and Stop(). We use this guard to
+  // control stopping and starting the audio thread.
+  // (2) Protect |render_callback_|.
+  base::Lock lock_;
+
   AudioDeviceThread audio_thread_;
-  std::unique_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
+  std::unique_ptr<AudioOutputDevice::AudioThreadCallback>
+      audio_thread_callback_;
+
+  RenderCallback* render_callback_;
 
   // Temporary hack to ignore OnStreamCreated() due to the user calling Stop()
   // so we don't start the audio thread pointing to a potentially freed
@@ -216,6 +223,8 @@ class MEDIA_EXPORT AudioOutputDevice
   const base::TimeDelta auth_timeout_;
   std::unique_ptr<base::OneShotTimer> auth_timeout_action_;
 
+  base::ThreadChecker control_thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 };