Add compositor support for the LatencyInfo.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 7b0a7e12cecbcf8304a840e1493d8237dc6c9aa7..8c8069b6ed7c5e624299988f730fe6d9da0b3aff 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1014,6 +1014,7 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
     return metadata;
 
   metadata.root_scroll_offset = RootScrollLayer()->TotalScrollOffset();
+  metadata.latency_info = latency_info_;
 
   return metadata;
 }
@@ -1113,7 +1114,13 @@ const RendererCapabilities& LayerTreeHostImpl::GetRendererCapabilities() const {
 bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
   if (frame.has_no_damage)
     return false;
-  return renderer_->SwapBuffers();
+  bool result = renderer_->SwapBuffers(latency_info_);
+  latency_info_.Clear();
+  return result;
+}
+
+void LayerTreeHostImpl::SetLatencyInfo(const LatencyInfo& latency_info) {
+  latency_info_.MergeWith(latency_info);
 }
 
 void LayerTreeHostImpl::EnableVSyncNotification(bool enable) {