SetPreviousFrameSurface should copy latency info to the new surface

cc/surfaces/surface.cc

Index: cc/surfaces/surface.cc
diff --git a/cc/surfaces/surface.cc b/cc/surfaces/surface.cc
index 63dd62cc1b005c286c2a5c369cbc91aad51a6c77..ab4bdb27d3c74284c7c97a8ec1af534931830c66 100644
--- a/cc/surfaces/surface.cc
+++ b/cc/surfaces/surface.cc
@@ -50,6 +50,13 @@ void Surface::SetPreviousFrameSurface(Surface* surface) {
   DCHECK(surface);
   frame_index_ = surface->frame_index() + 1;
   previous_frame_surface_id_ = surface->surface_id();
+  if (!surface->HasActiveFrame())
+    return;
+  active_frame_->metadata.latency_info.insert(

[jbauman, 2017/02/28 23:11:09]

Also check whether active_frame_ exists for the new surface.

[Fady Samuel, 2017/03/01 04:30:56]

I actually think that we might want to place the LatencyInfo on the pending
frame if there's no active frame or else it will get lost?

[Saman Sami, 2017/03/01 16:35:20]

A frame was just submitted, so either pending or active frame should exist.

+      active_frame_->metadata.latency_info.end(),
+      surface->active_frame_->metadata.latency_info.begin(),
+      surface->active_frame_->metadata.latency_info.end());
+  surface->active_frame_->metadata.latency_info.clear();
 }
 
 void Surface::QueueFrame(CompositorFrame frame, const DrawCallback& callback) {