Fix clang warnings on unused variable, mismatched tag, print format.

BUG: 20890093
Change-Id: I91588f481d80b69823bc9d104b8bd09167ee5373
diff --git a/media/jni/android_media_MediaSync.h b/media/jni/android_media_MediaSync.h
index fa5e5e0..5823057 100644
--- a/media/jni/android_media_MediaSync.h
+++ b/media/jni/android_media_MediaSync.h
@@ -26,7 +26,7 @@
 
 struct AudioPlaybackRate;
 class AudioTrack;
-struct IGraphicBufferProducer;
+class IGraphicBufferProducer;
 struct MediaClock;
 class MediaSync;