Do not pass the string device_id via IPC message to create an audio input stream

media/audio/audio_input_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 capturing class utilizing audio input stream provided
 // by a server (browser) process by use of an IPC interface.
 //
 // Relationship of classes:
 //
 //  AudioInputController                 AudioInputDevice
 //           ^                                  ^
 //           |                                  |
 //           v                  IPC             v
 // AudioInputRendererHost  <---------> AudioInputIPCDelegate
 //           ^                       (impl in AudioInputMessageFilter)
 //           |
 //           v
 // AudioInputDeviceManager
 //
 // Transportation of audio samples from the browser to the render process
 // is done by using shared memory in combination with a SyncSocket.
 // The AudioInputDevice user registers an AudioInputDevice::CaptureCallback by
 // calling Initialize().  The callback will be called with recorded audio from
 // the underlying audio layers.
 // The session ID is used by the AudioInputRendererHost to start the device
 // referenced by this ID.
 //
 // State sequences:
 //
-// Sequence where session_id has not been set using SetDevice():
-// ('<-' signifies callbacks, -> signifies calls made by AudioInputDevice)
 // Start -> InitializeOnIOThread -> CreateStream ->
 //       <- OnStreamCreated <-
 //       -> StartOnIOThread -> PlayStream ->
 //
-// Sequence where session_id has been set using SetDevice():
-// Start -> InitializeOnIOThread -> StartDevice ->
-//       <- OnDeviceReady <-
-//       -> CreateStream ->
-//       <- OnStreamCreated <-
-//       -> StartOnIOThread -> PlayStream ->
 //
 // AudioInputDevice::Capture => low latency audio transport on audio thread =>
 //                               |
 // Stop --> ShutDownOnIOThread ------>  CloseStream -> Close
 //
 // This class depends on two threads to function:
 //
 // 1. An IO thread.
 //    This thread is used to asynchronously process Start/Stop etc operations
 //    that are available via the public interface.  The public methods are
@@ skipping 34 matching lines @@
     : NON_EXPORTED_BASE(public AudioCapturerSource),
       NON_EXPORTED_BASE(public AudioInputIPCDelegate),
       NON_EXPORTED_BASE(public ScopedLoopObserver) {
  public:
   AudioInputDevice(AudioInputIPC* ipc,
                    const scoped_refptr<base::MessageLoopProxy>& io_loop);
 
   // AudioCapturerSource implementation.
   virtual void Initialize(const AudioParameters& params,
                           CaptureCallback* callback,
-                          CaptureEventHandler* event_handler) OVERRIDE;
+                          int session_id) OVERRIDE;
   virtual void Start() OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void SetVolume(double volume) OVERRIDE;
-  virtual void SetDevice(int session_id) OVERRIDE;
   virtual void SetAutomaticGainControl(bool enabled) OVERRIDE;
 
  protected:
   // Methods called on IO thread ----------------------------------------------
   // AudioInputIPCDelegate implementation.
   virtual void OnStreamCreated(base::SharedMemoryHandle handle,
                                base::SyncSocket::Handle socket_handle,
                                int length) OVERRIDE;
   virtual void OnVolume(double volume) OVERRIDE;
   virtual void OnStateChanged(
       AudioInputIPCDelegate::State state) OVERRIDE;
-  virtual void OnDeviceReady(const std::string& device_id) OVERRIDE;
   virtual void OnIPCClosed() OVERRIDE;
 
   friend class base::RefCountedThreadSafe<AudioInputDevice>;
   virtual ~AudioInputDevice();
 
  private:
   // 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 AudioInputMessageFilter and
   // sends IPC messages on that thread.
   void InitializeOnIOThread();
-  void SetSessionIdOnIOThread(int session_id);
   void StartOnIOThread();
   void ShutDownOnIOThread();
   void SetVolumeOnIOThread(double volume);
   void SetAutomaticGainControlOnIOThread(bool enabled);
 
   // MessageLoop::DestructionObserver implementation for the IO loop.
   // If the IO loop dies before we do, we shut down the audio thread from here.
   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 
   AudioParameters audio_parameters_;
 
   CaptureCallback* callback_;
-  CaptureEventHandler* event_handler_;
 
   AudioInputIPC* ipc_;
 
   // Our stream ID on the message filter. Only modified on the IO thread.
   int stream_id_;
 
   // The media session ID used to identify which input device to be started.
-  // Only modified on the IO thread.
+  // Only modified in Initialize() and ShutDownOnIOThread().
   int session_id_;
 
-  // State variable used to indicate it is waiting for a OnDeviceReady()
-  // callback. Only modified on the IO thread.
-  bool pending_device_ready_;
-
   // Stores the Automatic Gain Control state. Default is false.
   // Only modified on the IO thread.
   bool agc_is_enabled_;
 
   // 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_;
   AudioDeviceThread audio_thread_;
   scoped_ptr<AudioInputDevice::AudioThreadCallback> audio_callback_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioInputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_INPUT_DEVICE_H_