SF: Fix synthetic VSYNC after first powering on

After onActiveDisplayChangedLocked, isActiveDisplay was stale, so the
first powering on of a newly active display did not enable and resync
to hardware VSYNC, i.e. EventThread stayed in SyntheticVsync.

Also, merge EventThread APIs to enable/disable synthetic VSYNC.

Fixes: 264700488
Bug: 255635821
Test: dumpsys SurfaceFlinger --events
Change-Id: Ibd4099bb856adc11d887f3b7b9432fbc4cb2e33d
diff --git a/services/surfaceflinger/Scheduler/EventThread.cpp b/services/surfaceflinger/Scheduler/EventThread.cpp
index eb6d7e4..b78b92b 100644
--- a/services/surfaceflinger/Scheduler/EventThread.cpp
+++ b/services/surfaceflinger/Scheduler/EventThread.cpp
@@ -384,23 +384,13 @@
     return vsyncEventData;
 }
 
-void EventThread::onScreenReleased() {
+void EventThread::enableSyntheticVsync(bool enable) {
     std::lock_guard<std::mutex> lock(mMutex);
-    if (!mVSyncState || mVSyncState->synthetic) {
+    if (!mVSyncState || mVSyncState->synthetic == enable) {
         return;
     }
 
-    mVSyncState->synthetic = true;
-    mCondition.notify_all();
-}
-
-void EventThread::onScreenAcquired() {
-    std::lock_guard<std::mutex> lock(mMutex);
-    if (!mVSyncState || !mVSyncState->synthetic) {
-        return;
-    }
-
-    mVSyncState->synthetic = false;
+    mVSyncState->synthetic = enable;
     mCondition.notify_all();
 }