SF: Add a flag to guard the video detection feature

Video feature is still under development, so we should not be populating
layer history in scheduler if the feature is not turned on.

See go/surface-flinger-scheduler for more info

Test: manual
Bug: 123956502
Change-Id: I83eae3b5203a4e6b8976f9b7400711963eacbb34
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 220e664..2d9e230 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1075,6 +1075,7 @@
      * Scheduler
      */
     bool mUse90Hz = false;
+    bool mUseSmart90ForVideo = false;
     std::unique_ptr<Scheduler> mScheduler;
     sp<Scheduler::ConnectionHandle> mAppConnectionHandle;
     sp<Scheduler::ConnectionHandle> mSfConnectionHandle;