Enable pause/resume for RTSP streaming

When a stream is paused, RTSP Pause is also sent to the server.
Otherwise the buffering might continue until the memory runs out.
When the stream is resumed, RTSP Play will be sent in order to
resume the buffering.

Change-Id: I5dc1761140827c532451638c3fd3f34271e5b9ab
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
index df84123..8622abe 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
@@ -54,6 +54,8 @@
 
     virtual void start() = 0;
     virtual void stop() {}
+    virtual void pause() {}
+    virtual void resume() {}
 
     // Returns OK iff more data was available,
     // an error or ERROR_END_OF_STREAM if not.