Plumbing for getting FenceTracker timestamps

Change-Id: I1ebee9e42e28658bd3a2b161fdaabb7da756d8f3
diff --git a/services/surfaceflinger/FenceTracker.h b/services/surfaceflinger/FenceTracker.h
index 2fcc314..4cb14a5 100644
--- a/services/surfaceflinger/FenceTracker.h
+++ b/services/surfaceflinger/FenceTracker.h
@@ -29,7 +29,7 @@
 namespace android {
 
 class Layer;
-
+struct FrameTimestamps;
 /*
  * Keeps a circular buffer of fence/timestamp data for the last N frames in
  * SurfaceFlinger. Gets timestamps for fences after they have signaled.
@@ -40,6 +40,8 @@
      void dump(String8* outString);
      void addFrame(nsecs_t refreshStartTime, sp<Fence> retireFence,
              const Vector<sp<Layer>>& layers, sp<Fence> glDoneFence);
+     bool getFrameTimestamps(const Layer& layer, uint64_t frameNumber,
+             FrameTimestamps* outTimestamps);
 
 protected:
      static constexpr size_t MAX_FRAME_HISTORY = 8;