SurfaceFlinger: add win anim frame time tracking

This change makes the 'dumpsys SurfaceFlinger --latency' command with no extra
args dump the frame timestamp data for the most recent frames that
SurfaceFlinger generated that included window animation transaction changes.

Change-Id: I8bded1ea08a4cddefef0aa955401052bb9107c90
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index ef829ed..a82767b 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -129,6 +129,7 @@
 
     // thread-safe
     volatile int32_t mQueuedFrames;
+    FrameTracker mFrameTracker;
 
     // main thread
     sp<GraphicBuffer> mActiveBuffer;
@@ -138,7 +139,6 @@
     bool mCurrentOpacity;
     bool mRefreshPending;
     bool mFrameLatencyNeeded;
-    FrameTracker mFrameTracker;
 
     // constants
     PixelFormat mFormat;