SurfaceFlinger: add VSYNC-predicted as debug option

Add a trace point for the predicted VSYNC event.
This is controlled by debug.sf.show_predicted_vsync (default off)

Fixes: 150414668
Test: adb shell stop && adb shell setprop debug.sf.show_predicted_vsync 1 && adb shell start
Change-Id: Idd140dd2cb98c6bdd25197a742084cd5d4debd90
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.h b/services/surfaceflinger/Scheduler/VSyncReactor.h
index aa8a38d..7d8a8e3 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.h
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.h
@@ -30,6 +30,7 @@
 class VSyncDispatch;
 class VSyncTracker;
 class CallbackRepeater;
+class PredictedVsyncTracer;
 
 // TODO (b/145217110): consider renaming.
 class VSyncReactor : public android::DispSync {
@@ -86,6 +87,8 @@
 
     std::unordered_map<DispSync::Callback*, std::unique_ptr<CallbackRepeater>> mCallbacks
             GUARDED_BY(mMutex);
+
+    const std::unique_ptr<PredictedVsyncTracer> mPredictedVsyncTracer;
 };
 
 class SystemClock : public Clock {