update offloaded audio track sampling rate

AudioPlayer must read the sampling rate from offloaded audio sinks
whenever a new time position is computed as the decoder can update
the sampling rate on the fly.

Change-Id: I997e5248cfd4017aeceb4e11689324ded2a5bc88
diff --git a/include/media/MediaPlayerInterface.h b/include/media/MediaPlayerInterface.h
index cc244f0..26d8729 100644
--- a/include/media/MediaPlayerInterface.h
+++ b/include/media/MediaPlayerInterface.h
@@ -100,6 +100,7 @@
         virtual status_t    getFramesWritten(uint32_t *frameswritten) const = 0;
         virtual int         getSessionId() const = 0;
         virtual audio_stream_type_t getAudioStreamType() const = 0;
+        virtual uint32_t    getSampleRate() const = 0;
 
         // If no callback is specified, use the "write" API below to submit
         // audio data.