FlipperState debug logs improvement

Summary: Make it more explicit. What has succeeded, failed, started.

Reviewed By: ivanmisuno

Differential Revision: D49227799

fbshipit-source-id: fe9e6baaff227cf1db0b3150a3ee8cf194d2b6e6

xplat/Flipper/Log.h

@@ -22,3 +22,9 @@ void defaultLogHandler(const std::string& message);
 
 } // namespace flipper
 } // namespace facebook
+
+#if FLIPPER_DEBUG_LOG
+#define DEBUG_LOG(...) facebook::flipper::log(__VA_ARGS__)
+#else
+#define DEBUG_LOG(...)
+#endif