refactor AudioInputDevice to remove race condition.

content/renderer/media/audio_input_device.h

Index: content/renderer/media/audio_input_device.h
===================================================================
--- content/renderer/media/audio_input_device.h	(revision 95453)
+++ content/renderer/media/audio_input_device.h	(working copy)
@@ -21,17 +21,22 @@
 //
 // State sequences.
 //
-//            Task [IO thread]                  IPC [IO thread]
+//         [Capture thread]                [IO thread]
 //
-// Start -> InitializeOnIOThread -----> AudioInputHostMsg_CreateStream ------->
-//     <- OnLowLatencyCreated <- AudioInputMsg_NotifyLowLatencyStreamCreated <-
-//       ---> StartOnIOThread ---------> AudioInputHostMsg_PlayStream -------->
+//         StartOnCaptureThread  --> AddDelegateOnIOThread
+// DelegateAddedOnCaptureThread  <--
+//                               --> AudioInputHostMsg_CreateStream
+//                                   AudioInputMsg_NotifyLowLatencyStreamCreated
+// StartRecordingOnCaptureThread <-- OnLowLatencyCreated
+//                               --> AudioInputHostMsg_RecordStream
 //
 // AudioInputDevice::Capture => low latency audio transport on audio thread =>
 //                               |
-// Stop --> ShutDownOnIOThread ------>  AudioInputHostMsg_CloseStream -> Close
+//         StopOnCaptureThread  --> RemoveDelegateOnIOThread
+// DelegateRemovedOnCaptureThread <--
+//                                --> AudioInputHostMsg_CloseStream
 //
-// This class utilizes three threads during its lifetime, namely:
+// This class utilizes four threads during its lifetime, namely:
 // 1. Creating thread.
 //    Must be the main render thread. Start and Stop should be called on
 //    this thread.
@@ -42,6 +47,8 @@
 //    Responsible for calling the CaptrureCallback and feed audio samples from
 //    the audio layer in the browser process using sync sockets and shared
 //    memory.
+// 4. Capture thread.
+//    The main working thread on which AudioInputDevice runs its methods.
 
 #ifndef CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
 #define CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
@@ -55,7 +62,7 @@
 #include "base/threading/simple_thread.h"
 #include "content/renderer/media/audio_input_message_filter.h"
 
-struct AudioParameters;
+class AudioInputDeviceEventHandler;
 
 // TODO(henrika): This class is based on the AudioDevice class and it has
 // many components in common. Investigate potential for re-factoring.
@@ -74,9 +81,12 @@
   };
 
   // Methods called on main render thread -------------------------------------
+  // |message_loop_proxy| is the working thread for AudioInputDevice.
   AudioInputDevice(size_t buffer_size,
                    int channels,
                    double sample_rate,
+                   base::MessageLoopProxy* message_loop_proxy,
+                   AudioInputDeviceEventHandler* event_handler,
                    CaptureCallback* callback);
   virtual ~AudioInputDevice();
 
@@ -105,15 +115,26 @@
   virtual void OnVolume(double volume);
 
  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(const AudioParameters& params);
-  void StartOnIOThread();
-  void ShutDownOnIOThread();
-  void SetVolumeOnIOThread(double volume);
+  enum State {
+    kStarting,
+    kStarted,
+    kPaused,
+    kStopped,
+    kStopping,
+    kError,
+  };
 
+  // Methods called on main working thread for AudioInputDevice ---------------
+  // The following methods are tasks posted on capture thread that needs to
+  // be executed on that thread.
+  void StartOnCaptureThread();
+  void StartRecordingOnCaptureThread(base::SharedMemoryHandle handle,
+                                     base::SyncSocket::Handle socket_handle,
+                                     uint32 length);
+  void StopOnCaptureThread();
+  void SetVolumeOnCaptureThread(double volume);
+  void OnDelegateAddedOnCaptureThread(int32 stream_id);
+  void OnDelegateRemovedOnCaptureThread();
   void Send(IPC::Message* message);
 
   // Method called on the audio thread ----------------------------------------
@@ -123,6 +144,15 @@
   // DelegateSimpleThread::Delegate implementation.
   virtual void Run();
 
+  // Add/Remove delegate on IO thread------------------------------------------
+  void AddDelegateOnIOThread();
+  void RemoveDelegateOnIOThread(int32 stream_id);
+
+  // IPC message stuff.
+  base::SharedMemory* shared_memory() { return shared_memory_.get(); }
+  base::SyncSocket* socket() { return socket_.get(); }
+  void* shared_memory_data() { return shared_memory()->memory(); }
+
   // Format
   size_t buffer_size_;  // in sample-frames
   int channels_;
@@ -130,6 +160,7 @@
   double sample_rate_;
 
   CaptureCallback* callback_;
+  AudioInputDeviceEventHandler* event_handler_;
 
   // The client callback receives captured audio here.
   std::vector<float*> audio_data_;
@@ -142,14 +173,14 @@
   // The current volume scaling [0.0, 1.0] of the audio stream.
   double volume_;
 
+  // The working thread for AudioInputDevice.
+  scoped_refptr<base::MessageLoopProxy> capture_message_loop_proxy_;
+
+  State state_;
+
   // Callbacks for capturing audio occur on this thread.
   scoped_ptr<base::DelegateSimpleThread> audio_thread_;
 
-  // IPC message stuff.
-  base::SharedMemory* shared_memory() { return shared_memory_.get(); }
-  base::SyncSocket* socket() { return socket_.get(); }
-  void* shared_memory_data() { return shared_memory()->memory(); }
-
   // Cached audio input message filter (lives on the main render thread).
   scoped_refptr<AudioInputMessageFilter> filter_;