Add a DequeueReady FrameEvent

Test: adb shell /data/nativetest/libgui_test/libgui_test
--gtest_filter=*GetFrameTimestamps*

Change-Id: I98ffd4123fc50b5f560e432f4078408c913c8edf
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index c3eab37..92d2292 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -286,7 +286,7 @@
 
 #ifdef USE_HWC2
     // If a buffer was replaced this frame, release the former buffer
-    void releasePendingBuffer();
+    void releasePendingBuffer(nsecs_t dequeueReadyTime);
 #endif
 
     /*