Cleanup AudioDeviceThread to reduce locking and unused features.

media/audio/audio_device_thread.h

Index: media/audio/audio_device_thread.h
diff --git a/media/audio/audio_device_thread.h b/media/audio/audio_device_thread.h
index 1ffefc5a29146738e7a3274a2e9b1ef70e0a583a..f3287ef39ccf86705642dc5439f7b13860737f1d 100644
--- a/media/audio/audio_device_thread.h
+++ b/media/audio/audio_device_thread.h
@@ -8,31 +8,21 @@
 #include <stdint.h>
 
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/sync_socket.h"
-#include "base/synchronization/lock.h"
+#include "base/threading/platform_thread.h"
 #include "base/threading/thread_checker.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
-namespace base {
-class MessageLoop;
-}
-
 namespace media {
-class AudioBus;
 
 // Data transfer between browser and render process uses a combination
 // of sync sockets and shared memory. To read from the socket and render
 // data, we use a worker thread, a.k.a. the AudioDeviceThread, which reads
 // data from the browser via the socket and fills the shared memory from the
 // audio thread via the AudioDeviceThread::Callback interface/class.
-// For more details see the documentation in audio_device.h.
-//
-// TODO(tommi): Multiple audio input/output device instances should be able to
-// share the same thread instead of spinning one per instance.
-class MEDIA_EXPORT AudioDeviceThread {
+class MEDIA_EXPORT AudioDeviceThread : public base::PlatformThread::Delegate {
  public:
   // This is the callback interface/base class that Audio[Output|Input]Device
   // implements to render input/output data. The callbacks run on the
@@ -43,7 +33,6 @@ class MEDIA_EXPORT AudioDeviceThread {
              base::SharedMemoryHandle memory,
              int memory_length,
              int total_segments);
-    virtual ~Callback();
 
     // One time initialization for the callback object on the audio thread.
     void InitializeOnAudioThread();
@@ -56,18 +45,17 @@ class MEDIA_EXPORT AudioDeviceThread {
     virtual void Process(uint32_t pending_data) = 0;
 
    protected:
+    virtual ~Callback();
+
     // Protected so that derived classes can access directly.
     // The variables are 'const' since values are calculated/set in the
     // constructor and must never change.
     const AudioParameters audio_parameters_;
-    const double samples_per_ms_;
-    const double bytes_per_ms_;
-    const uint32_t bytes_per_frame_;
 
     base::SharedMemory shared_memory_;
     const int memory_length_;
     const int total_segments_;
-    int segment_length_;
+    const int segment_length_;
 
     // Detached in constructor and attached in InitializeOnAudioThread() which
     // is called on the audio device thread. Sub-classes can then use it for
@@ -78,43 +66,22 @@ class MEDIA_EXPORT AudioDeviceThread {
     DISALLOW_COPY_AND_ASSIGN(Callback);
   };
 
-  AudioDeviceThread();
-  ~AudioDeviceThread();
-
-  // Starts the audio thread. The thread must not already be running.  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);
-
-  // 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);
-
-  // Returns true if the thread is stopped or stopping.
-  bool IsStopped();
+  // Creates and automatically starts the audio thread.
+  AudioDeviceThread(Callback* callback,
+                    base::SyncSocket::Handle socket,
+                    const char* thread_name);
+
+  // This tells the audio thread to stop and clean up the data; this is a
+  // synchronous process and the thread will stop before the method returns.
+  ~AudioDeviceThread() override;
 
  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.
-  class Thread;
-
-  base::Lock thread_lock_;
-  scoped_refptr<AudioDeviceThread::Thread> thread_;
+  void ThreadMain() final;
+
+  Callback* const callback_;
+  const char* thread_name_;
+  base::CancelableSyncSocket socket_;
+  base::PlatformThreadHandle thread_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDeviceThread);
 };