Finer synchronization for nuplayer stats

Bug: 131474028
Test: manual
Change-Id: I4c38cc979baa91d6d23115da1d53c8152e77cb36
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDecoderBase.h b/media/libmediaplayerservice/nuplayer/NuPlayerDecoderBase.h
index d44c396..a3e0046 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDecoderBase.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDecoderBase.h
@@ -47,7 +47,7 @@
     void signalResume(bool notifyComplete);
     void initiateShutdown();
 
-    virtual sp<AMessage> getStats() const {
+    virtual sp<AMessage> getStats() {
         return mStats;
     }
 
@@ -88,6 +88,7 @@
     int32_t mBufferGeneration;
     bool mPaused;
     sp<AMessage> mStats;
+    Mutex mStatsLock;
 
 private:
     enum {