Protect against possible race conditions

Test: make cts -j123 && cts-tradefed run cts-dev -m \
CtsMediaTestCases --compatibility:module-arg \
CtsMediaTestCases:include-annotation:\
android.platform.test.annotations.RequiresDevice

Test: Run the poc in b/38234812

Bug: 38234812
Change-Id: I28322e5a812c02c8e449ab8773715f60b9f5d976
diff --git a/media/libmediaplayerservice/MediaPlayerService.h b/media/libmediaplayerservice/MediaPlayerService.h
index 06b9cad..e35d098 100644
--- a/media/libmediaplayerservice/MediaPlayerService.h
+++ b/media/libmediaplayerservice/MediaPlayerService.h
@@ -362,7 +362,7 @@
 
 
         sp<MediaPlayerBase>     setDataSource_pre(player_type playerType);
-        void                    setDataSource_post(const sp<MediaPlayerBase>& p,
+        status_t                setDataSource_post(const sp<MediaPlayerBase>& p,
                                                    status_t status);
 
         static  void            notify(void* cookie, int msg,
@@ -404,7 +404,7 @@
             wp<MediaPlayerBase> mListener;
         };
 
-        void clearDeathNotifiers();
+        void clearDeathNotifiers_l();
 
         friend class MediaPlayerService;
                                 Client( const sp<MediaPlayerService>& service,
@@ -433,7 +433,7 @@
         void addNewMetadataUpdate(media::Metadata::Type type);
 
         // Disconnect from the currently connected ANativeWindow.
-        void disconnectNativeWindow();
+        void disconnectNativeWindow_l();
 
         status_t setAudioAttributes_l(const Parcel &request);