device/bluetooth: Add I/O watcher for audio data retrieval triggered by state change.

device/bluetooth/bluetooth_audio_sink.h

Index: device/bluetooth/bluetooth_audio_sink.h
diff --git a/device/bluetooth/bluetooth_audio_sink.h b/device/bluetooth/bluetooth_audio_sink.h
index 6abb8a5d14e43909ab140d00845ff152df95fa09..fac0308c5f92b69a69d8acd4bddb6aa67bdf5d84 100644
--- a/device/bluetooth/bluetooth_audio_sink.h
+++ b/device/bluetooth/bluetooth_audio_sink.h
@@ -73,9 +73,12 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAudioSink
         BluetoothAudioSink* audio_sink,
         uint16_t volume) = 0;
 
-    // TODO(mcchou): Add method to monitor the availability of audio data during
-    // the streaming. This method should associate with BluetoothAudioSink
-    // specific IOBuffer wrapping fd, read_mtu and write_mtu.
+    // Callled when there is audio data available. |audio_sink| indicates the

[armansito, 2015/03/12 03:42:55]

nit: Called

[Miao, 2015/03/12 22:33:32]

Done.

+    // object being changed. |data| is the pointer to the audio data and |size|
+    // is the number of the bytes in |data|.

[armansito, 2015/03/12 03:42:55]

I would explain here that this method provides the raw audio data which hasn't
been processed or assembled in any way and that the RTP units and SBC decoding
needs to happen here.

[armansito, 2015/03/12 03:42:55]

nit: s/number of the bytes/number of bytes/

[Miao, 2015/03/12 22:33:31]

Done.

+    virtual void BluetoothAudioSinkDataAvailable(BluetoothAudioSink* audio_sink,
+                                                 char* data,
+                                                 size_t size) = 0;
   };
 
   // The ErrorCallback is used for the methods that can fail in which case it