stagefright: warnings be gone, some are now errors, use clang

Change-Id: I81f438ae444f04c12ae27ae4ef6d073033de172c
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
index 1b0c2df..ef1ba13 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerSource.h
@@ -28,7 +28,7 @@
 namespace android {
 
 struct ABuffer;
-struct MediaBuffer;
+class MediaBuffer;
 
 struct NuPlayer::Source : public AHandler {
     enum Flags {