not for commit/review (thread cost tracker)

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 54a16aa819d946c0c28f5545452285a0913cee22..e4780bfa8ecbcfd14b2e144296bf1e8ed0d5ff0c 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -19,6 +19,7 @@
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/synced_property.h"
+#include "cc/debug/frame_timing_cost_tracker.h"
 #include "cc/debug/micro_benchmark_controller_impl.h"
 #include "cc/input/input_handler.h"
 #include "cc/input/layer_scroll_offset_delegate.h"
@@ -727,6 +728,8 @@ class CC_EXPORT LayerTreeHostImpl
   bool requires_high_res_to_draw_;
   bool required_for_draw_tile_is_top_of_raster_queue_;
 
+  FrameTimingCostTracker frame_timing_cost_tracker_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };