Fix warnings about unused parameters

Change-Id: I27dc108e2c1f7ffd414bb7ff3d4c349651da6c26
diff --git a/media/libmediaplayerservice/MediaPlayerService.h b/media/libmediaplayerservice/MediaPlayerService.h
index 65b28dc..fc355b0 100644
--- a/media/libmediaplayerservice/MediaPlayerService.h
+++ b/media/libmediaplayerservice/MediaPlayerService.h
@@ -211,12 +211,12 @@
         virtual void            flush() {}
         virtual void            pause() {}
         virtual void            close() {}
-                void            setAudioStreamType(audio_stream_type_t streamType) {}
+                void            setAudioStreamType(audio_stream_type_t streamType __unused) {}
                 // stream type is not used for AudioCache
         virtual audio_stream_type_t getAudioStreamType() const { return AUDIO_STREAM_DEFAULT; }
 
-                void            setVolume(float left, float right) {}
-        virtual status_t        setPlaybackRatePermille(int32_t ratePermille) { return INVALID_OPERATION; }
+                void            setVolume(float left __unused, float right __unused) {}
+        virtual status_t        setPlaybackRatePermille(int32_t ratePermille __unused) { return INVALID_OPERATION; }
                 uint32_t        sampleRate() const { return mSampleRate; }
                 audio_format_t  format() const { return mFormat; }
                 size_t          size() const { return mSize; }