Use audio_session_t consistently

Bug: 27562099
Change-Id: I328d8226191386b163f2ace41233607294c50dcd
diff --git a/include/media/MediaPlayerInterface.h b/include/media/MediaPlayerInterface.h
index 9e5056f..54862d1 100644
--- a/include/media/MediaPlayerInterface.h
+++ b/include/media/MediaPlayerInterface.h
@@ -101,7 +101,7 @@
         virtual status_t    getTimestamp(AudioTimestamp &ts) const = 0;
         virtual int64_t     getPlayedOutDurationUs(int64_t nowUs) const = 0;
         virtual status_t    getFramesWritten(uint32_t *frameswritten) const = 0;
-        virtual int         getSessionId() const = 0;
+        virtual audio_session_t getSessionId() const = 0;
         virtual audio_stream_type_t getAudioStreamType() const = 0;
         virtual uint32_t    getSampleRate() const = 0;