SurfaceFlinger: no app vsyncs during config switch

Do not dipatch vsync callbacks to applications during a config
switch as applications will get choreographer callbacks at uneven
times and will stuff the queue to surface flinger.

Test: test google/perf/jank/UIBench/UIBench-Trace:com.android.uibench.janktests.UiBenchJankTests#testClippedListView -v
Change-Id: I0537933c27af83a9186bcff54c3596d612c748ea
diff --git a/services/surfaceflinger/Scheduler/InjectVSyncSource.h b/services/surfaceflinger/Scheduler/InjectVSyncSource.h
index a0e1447..90609af 100644
--- a/services/surfaceflinger/Scheduler/InjectVSyncSource.h
+++ b/services/surfaceflinger/Scheduler/InjectVSyncSource.h
@@ -44,6 +44,7 @@
 
     void setVSyncEnabled(bool) override {}
     void setPhaseOffset(nsecs_t) override {}
+    void pauseVsyncCallback(bool) {}
 
 private:
     std::mutex mCallbackMutex;