mediaplayer: support dynamic playback rate

Bug: 19196501

Change-Id: I856b1507d5fa2cedfb645706d2435683a7d3e050
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDriver.h b/media/libmediaplayerservice/nuplayer/NuPlayerDriver.h
index 5cba7d9..e53abcd 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDriver.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDriver.h
@@ -47,6 +47,7 @@
     virtual status_t stop();
     virtual status_t pause();
     virtual bool isPlaying();
+    virtual status_t setPlaybackRate(float rate);
     virtual status_t seekTo(int msec);
     virtual status_t getCurrentPosition(int *msec);
     virtual status_t getDuration(int *msec);