Add -Wthread-safety in libmediautils

Bug: 268360578
Test: m
Change-Id: I2532cf19e6e56e5c36c1c31c6326971377bf1415
diff --git a/media/utils/include/mediautils/TimerThread.h b/media/utils/include/mediautils/TimerThread.h
index d5be177..d84d682 100644
--- a/media/utils/include/mediautils/TimerThread.h
+++ b/media/utils/include/mediautils/TimerThread.h
@@ -340,7 +340,7 @@
                 std::pair<std::shared_ptr<const Request>, TimerCallback>>
                         mSecondChanceRequests GUARDED_BY(mMutex);
 
-        RequestQueue& mTimeoutQueue; // locked internally, added to when request times out.
+        RequestQueue& mTimeoutQueue GUARDED_BY(mMutex); // added to when request times out.
 
         // Worker thread variables
         bool mShouldExit GUARDED_BY(mMutex) = false;