not for commit/review (thread cost tracker)

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 c9d76c622095c56b0f7f92d7190d879eeba15aef..38d7553d063744b31f69cbb02e934adb7cc88b17 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -302,6 +302,8 @@ void LayerTreeHostImpl::CommitComplete() {
     pending_tree_->ApplyScrollDeltasSinceBeginMainFrame();
   sync_tree()->set_needs_update_draw_properties();
 
+  frame_timing_cost_tracker_.ResetCost();
+  frame_timing_cost_tracker_.Start(sync_tree()->source_frame_number());
   if (settings_.impl_side_painting) {
     // Impl-side painting needs an update immediately post-commit to have the
     // opportunity to create tilings.  Other paths can call UpdateDrawProperties
@@ -1838,6 +1840,8 @@ void LayerTreeHostImpl::ActivateSyncTree() {
         pending_page_scale_animation->scale,
         pending_page_scale_animation->duration);
   }
+
+  // frame_timing_cost_tracker_.GetTotalCost().InSecondsF());
 }
 
 void LayerTreeHostImpl::SetVisible(bool visible) {
@@ -1966,7 +1970,8 @@ void LayerTreeHostImpl::CreateAndSetTileManager() {
                                     : settings_.scheduled_raster_task_limit;
   tile_manager_ = TileManager::Create(
       this, task_runner, resource_pool_.get(),
-      tile_task_worker_pool_->AsTileTaskRunner(), scheduled_raster_task_limit);
+      tile_task_worker_pool_->AsTileTaskRunner(), scheduled_raster_task_limit,
+      frame_timing_cost_tracker_.GetWorkerThreadCostTracker());
 
   UpdateTileManagerMemoryPolicy(ActualManagedMemoryPolicy());
 }