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

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index b5cb8592aacf260599406b921ecde77e97bbc939..8276479a347ea5f7749a6c4513f6a2b0e5e92af6 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -416,6 +416,12 @@ void LayerTreeHost::CommitComplete() {
   }
 }
 
+void LayerTreeHost::DidCommitAndDrawFrame() {
+  client_->DidCommitAndDrawFrame();
+  if (animation_host_)
+    animation_host_->ReportAndClearStatsOnFrameEnd();
+}
+
 void LayerTreeHost::SetOutputSurface(scoped_ptr<OutputSurface> surface) {
   TRACE_EVENT0("cc", "LayerTreeHost::SetOutputSurface");
   DCHECK(output_surface_lost_);
@@ -1186,6 +1192,7 @@ void LayerTreeHost::AnimateLayers(base::TimeTicks monotonic_time) {
   if (animation_host_) {
     if (animation_host_->AnimateLayers(monotonic_time))
       animation_host_->UpdateAnimationState(true, &events);
+    ReportAndClearStatsAfterAnimateLayers();
   } else if (animation_registrar_) {
     if (animation_registrar_->AnimateLayers(monotonic_time))
       animation_registrar_->UpdateAnimationState(true, &events);
@@ -1330,7 +1337,9 @@ void LayerTreeHost::SetAuthoritativeVSyncInterval(
 }
 
 Layer* LayerTreeHost::LayerById(int id) const {
+  base::TimeTicks start_time = base::TimeTicks::Now();
   LayerIdMap::const_iterator iter = layer_id_map_.find(id);
+  find_layer_by_id_stats_ += base::TimeTicks::Now() - start_time;
   return iter != layer_id_map_.end() ? iter->second : NULL;
 }
 
@@ -1457,4 +1466,11 @@ bool LayerTreeHost::HasActiveAnimation(const Layer* layer) const {
                          : false;
 }
 
+void LayerTreeHost::ReportAndClearStatsAfterAnimateLayers() {
+  LOCAL_HISTOGRAM_CUSTOM_COUNTS("Mutators.FindLayerById",
+                                find_layer_by_id_stats_.InMicroseconds(), 1,
+                                1000, 10);
+  find_layer_by_id_stats_ = base::TimeDelta();
+}
+
 }  // namespace cc