Plumbing for getting FenceTracker timestamps

Change-Id: I1ebee9e42e28658bd3a2b161fdaabb7da756d8f3
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 79750a6..fef2d98 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -409,6 +409,11 @@
 
     std::vector<OccupancyTracker::Segment> getOccupancyHistory(bool forceFlush);
 
+    bool getFrameTimestamps(uint64_t frameNumber,
+            FrameTimestamps* outTimestamps) const {
+        return mFlinger->getFrameTimestamps(*this, frameNumber, outTimestamps);
+    }
+
 protected:
     // constant
     sp<SurfaceFlinger> mFlinger;