hack up frame latency measurement

Change-Id: I6d9a466a23285304f0e229a5649815636ab5d6af
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index af47402..b295201 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -445,6 +445,12 @@
     const nsecs_t now = systemTime();
     mDebugInSwapBuffers = now;
     hw.flip(mSwapRegion);
+
+    size_t numLayers = mVisibleLayersSortedByZ.size();
+    for (size_t i = 0; i < numLayers; i++) {
+        mVisibleLayersSortedByZ[i]->onLayerDisplayed();
+    }
+
     mLastSwapBufferTime = systemTime() - now;
     mDebugInSwapBuffers = 0;
     mSwapRegion.clear();