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/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index b99b859..69fd18d 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -375,10 +375,10 @@
 
     static inline std::atomic<AudioFlinger *> gAudioFlinger = nullptr;
 
-    sp<SyncEvent> createSyncEvent(AudioSystem::sync_event_t type,
+    sp<audioflinger::SyncEvent> createSyncEvent(AudioSystem::sync_event_t type,
                                         audio_session_t triggerSession,
                                         audio_session_t listenerSession,
-                                        sync_event_callback_t callBack,
+                                        audioflinger::SyncEventCallback callBack,
                                         const wp<RefBase>& cookie);
 
     bool        btNrecIsOff() const { return mBtNrecIsOff.load(); }
@@ -939,8 +939,8 @@
                 bool        masterMute_l() const;
                 AudioHwDevice* loadHwModule_l(const char *name);
 
-                Vector < sp<SyncEvent> > mPendingSyncEvents; // sync events awaiting for a session
-                                                             // to be created
+                // sync events awaiting for a session to be created.
+                std::list<sp<audioflinger::SyncEvent>> mPendingSyncEvents;
 
                 // Effect chains without a valid thread
                 DefaultKeyedVector< audio_session_t , sp<EffectChain> > mOrphanEffectChains;