[DRAFT] Animations: Profile hash look-ups for external mutators

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 9dc331f2bdc4e69301efd8aca4b48084732f602a..e9f02d71bfbf1a70a52179318eb0164ea2909375 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1732,6 +1732,8 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
     }
   }
   renderer_->SwapBuffers(metadata);
+  if (animation_host_)
+    animation_host_->ReportAndClearStatsOnFrameEnd();
   return true;
 }
 
@@ -3123,6 +3125,7 @@ void LayerTreeHostImpl::AnimateLayers(base::TimeTicks monotonic_time) {
   if (animation_host_) {
     if (animation_host_->AnimateLayers(monotonic_time))
       SetNeedsAnimate();
+    ReportAndClearStatsAfterAnimateLayers();
   } else {
     if (animation_registrar_->AnimateLayers(monotonic_time))
       SetNeedsAnimate();
@@ -3617,4 +3620,23 @@ gfx::ScrollOffset LayerTreeHostImpl::GetScrollOffsetForAnimation(
   return gfx::ScrollOffset();
 }
 
+void LayerTreeHostImpl::ReportAndClearStatsAfterAnimateLayers() {
+  base::TimeDelta find_layer_by_id_stats =
+      active_tree_->find_layer_by_id_stats();
+  active_tree_->ClearStatsOnFrameEnd();
+
+  if (pending_tree_) {
+    find_layer_by_id_stats += pending_tree_->find_layer_by_id_stats();
+    pending_tree_->ClearStatsOnFrameEnd();
+  }
+  if (recycle_tree_) {
+    find_layer_by_id_stats += recycle_tree_->find_layer_by_id_stats();
+    recycle_tree_->ClearStatsOnFrameEnd();
+  }
+
+  LOCAL_HISTOGRAM_CUSTOM_COUNTS("Mutators.FindLayerImplById",
+                                find_layer_by_id_stats.InMicroseconds(), 1,
+                                1000, 10);
+}
+
 }  // namespace cc