Remove "high"-latency audio code path

content/renderer/media/audio_device.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.
 //
 // Low-latency audio rendering unit utilizing audio output stream provided
 // by browser process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioOutputController                AudioDevice
 //           ^                                ^
 //           |                                |
 //           v               IPC              v
 //    AudioRendererHost  <---------> AudioMessageFilter
 //
 // Transportation of audio samples from the render to the browser process
 // is done by using shared memory in combination with a sync socket pair
 // to generate a low latency transport. The AudioDevice user registers an
 // AudioDevice::RenderCallback at construction and will be polled by the

[scherkus (not reviewing), 2012/02/01 22:56:12]

update docs?

[vrk (LEFT CHROMIUM), 2012/02/02 21:05:41]

Changed a few words, but otherwise these comments seem accurate still. Let me
know if there was something else you were concerned about here!

 // AudioDevice for audio to be played out by the underlying audio layers.
 //
 // State sequences.
 //
 //            Task [IO thread]                  IPC [IO thread]
 //
 // Start -> InitializeOnIOThread ------> AudioHostMsg_CreateStream -------->
-//       <- OnLowLatencyCreated <- AudioMsg_NotifyLowLatencyStreamCreated <-
+//       <- OnStreamCreated <- AudioMsg_NotifyStreamCreated <-
 //       ---> PlayOnIOThread -----------> AudioHostMsg_PlayStream -------->
 //
 // Optionally Play() / Pause() sequences may occur:
 // Play -> PlayOnIOThread --------------> AudioHostMsg_PlayStream --------->
 // Pause -> PauseOnIOThread ------------> AudioHostMsg_PauseStream -------->
-// (note that Play() / Pause() sequences before OnLowLatencyCreated are
-//  deferred until OnLowLatencyCreated, with the last valid state being used)
+// (note that Play() / Pause() sequences before OnStreamCreated are
+//  deferred until OnStreamCreated, with the last valid state being used)
 //
 // AudioDevice::Render => audio transport on audio thread with low latency =>
 //                               |
 // Stop --> ShutDownOnIOThread -------->  AudioHostMsg_CloseStream -> Close
 //
 // This class utilizes several threads during its lifetime, namely:
 // 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()
@@ skipping 80 matching lines @@
   virtual bool SetVolume(double volume) OVERRIDE;
 
   // Gets the playback volume, with range [0.0, 1.0] inclusive.
   virtual void GetVolume(double* volume) OVERRIDE;
 
   double sample_rate() const { return sample_rate_; }
   size_t buffer_size() const { return buffer_size_; }
 
   // Methods called on IO thread ----------------------------------------------
   // AudioMessageFilter::Delegate methods, called by AudioMessageFilter.
-  virtual void OnRequestPacket(AudioBuffersState buffers_state) OVERRIDE;
   virtual void OnStateChanged(AudioStreamState state) OVERRIDE;
-  virtual void OnCreated(base::SharedMemoryHandle handle,
-                         uint32 length) OVERRIDE;
-  virtual void OnLowLatencyCreated(base::SharedMemoryHandle handle,
-                                   base::SyncSocket::Handle socket_handle,
-                                   uint32 length) OVERRIDE;
-  virtual void OnVolume(double volume) OVERRIDE;
+  virtual void OnStreamCreated(base::SharedMemoryHandle handle,
+                               base::SyncSocket::Handle socket_handle,
+                               uint32 length) OVERRIDE;
 
  private:
   // Magic required by ref_counted.h to avoid any code deleting the object
   // accidentally while there are references to it.
   friend class base::RefCountedThreadSafe<AudioDevice>;
   virtual ~AudioDevice();
 
   // Methods called on IO thread ----------------------------------------------
   // The following methods are tasks posted on the IO thread that needs to
   // be executed on that thread. They interact with AudioMessageFilter and
@@ skipping 47 matching lines @@
   // Must only be modified on the IO thread and when the thread is not running.
   scoped_ptr<base::DelegateSimpleThread> audio_thread_;
 
   // Cached audio message filter (lives on the main render thread).
   scoped_refptr<AudioMessageFilter> filter_;
 
   // Our stream ID on the message filter. Only accessed on the IO thread.
   // Must only be modified on the IO thread.
   int32 stream_id_;
 
-  // State of Play() / Pause() calls before OnLowLatencyCreated() is called.
+  // State of Play() / Pause() calls before OnStreamCreated() is called.
   bool play_on_start_;
 
-  // Set to |true| when OnLowLatencyCreated() is called.
+  // Set to |true| when OnStreamCreated() is called.
   // Set to |false| when ShutDownOnIOThread() is called.
   // This is for use with play_on_start_ to track Play() / Pause() state.
   // Must only be touched from the IO thread.
   bool is_started_;
 
   // Data transfer between browser and render process uses a combination
   // of sync sockets and shared memory to provide lowest possible latency.
   // These variables must only be set on the IO thread while the audio_thread_
   // is not running.
   base::SharedMemoryHandle shared_memory_handle_;
   scoped_ptr<base::CancelableSyncSocket> audio_socket_;
   int memory_length_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDevice);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_H_