Fix start/stop of html5 audio stream and race condition when pausing.

content/renderer/media/audio_device.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.
 //
 // Low-latency audio rendering unit utilizing audio output stream provided
 // by browser process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioOutputController                AudioDevice
@@ skipping 63 matching lines @@
 #include "content/renderer/media/audio_message_filter.h"
 #include "media/audio/audio_parameters.h"
 
 class CONTENT_EXPORT AudioDevice
     : public AudioMessageFilter::Delegate,
       public base::DelegateSimpleThread::Delegate,
       public base::RefCountedThreadSafe<AudioDevice> {
  public:
   class CONTENT_EXPORT RenderCallback {
    public:
-    virtual void Render(const std::vector<float*>& audio_data,
-                        size_t number_of_frames,
-                        size_t audio_delay_milliseconds) = 0;
+    // Fills entire buffer of length |number_of_frames| but returns actual
+    // number of frames it got from its source (|number_of_frames| in case of
+    // continuous stream). That actual number of frames is passed to host
+    // together with PCM audio data and host is free to use or ignore it.
+    virtual size_t Render(const std::vector<float*>& audio_data,
+                          size_t number_of_frames,
+                          size_t audio_delay_milliseconds) = 0;
    protected:
     virtual ~RenderCallback() {}
   };
 
   // Methods called on main render thread -------------------------------------
 
   // Minimal constructor where Initialize() must be called later.
   AudioDevice();
 
   AudioDevice(size_t buffer_size,
@@ skipping 55 matching lines @@
   // be executed on that thread. They interact with AudioMessageFilter and
   // sends IPC messages on that thread.
   void InitializeOnIOThread(const AudioParameters& params);
   void PlayOnIOThread();
   void PauseOnIOThread(bool flush);
   void ShutDownOnIOThread(base::WaitableEvent* completion);
   void SetVolumeOnIOThread(double volume);
 
   void Send(IPC::Message* message);
 
-  // Method called on the audio thread (+ one call on the IO thread) ----------
-  // Calls the client's callback for rendering audio. There will also be one
-  // initial call on the IO thread before the audio thread has been created.
-  void FireRenderCallback(int16* data);
+  // Method called on the audio thread ----------------------------------------
+  // Calls the client's callback for rendering audio.
+  // Returns actual number of filled frames that callback returned. This length
+  // is passed to host at the end of the shared memory (i.e. buffer). In case of
+  // continuous stream host just ignores it and assumes buffer is always filled
+  // to its capacity.
+  size_t FireRenderCallback(int16* data);
 
   // DelegateSimpleThread::Delegate implementation.
   virtual void Run() OVERRIDE;
 
   // Closes socket and joins with the audio thread.
   void ShutDownAudioThread();
 
   // Format
   size_t buffer_size_;  // in sample-frames
   int channels_;
@@ skipping 42 matching lines @@
 
   // Protects lifetime of:
   // socket_handle_
   // audio_thread_
   base::Lock lock_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDevice);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_H_