libmediaplayerservice: fix warnings, make warnings errors, use clang

Change-Id: I1b2f6b65c5abbc366068a60b8909104f31b94228
diff --git a/media/libmediaplayerservice/RemoteDisplay.h b/media/libmediaplayerservice/RemoteDisplay.h
index 82a0116..1a48981 100644
--- a/media/libmediaplayerservice/RemoteDisplay.h
+++ b/media/libmediaplayerservice/RemoteDisplay.h
@@ -28,7 +28,7 @@
 
 struct ALooper;
 struct ANetworkSession;
-struct IRemoteDisplayClient;
+class IRemoteDisplayClient;
 struct WifiDisplaySource;
 
 struct RemoteDisplay : public BnRemoteDisplay {