SyncEvent: modernize C++

And add unit test mediasyncevent_tests.

Test: atest mediasyncevent_tests
Bug: 283021652
Merged-In: I37711f4271c68042f178db9370549c0c3260ace8
Change-Id: I37711f4271c68042f178db9370549c0c3260ace8
diff --git a/services/audioflinger/PlaybackTracks.h b/services/audioflinger/PlaybackTracks.h
index 33983d7..efcd832 100644
--- a/services/audioflinger/PlaybackTracks.h
+++ b/services/audioflinger/PlaybackTracks.h
@@ -131,7 +131,7 @@
 // implement FastMixerState::VolumeProvider interface
     virtual gain_minifloat_packed_t getVolumeLR();
 
-    virtual status_t    setSyncEvent(const sp<SyncEvent>& event);
+            status_t    setSyncEvent(const sp<audioflinger::SyncEvent>& event) override;
 
     virtual bool        isFastTrack() const { return (mFlags & AUDIO_OUTPUT_FLAG_FAST) != 0; }