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

cc/animation/animation_host.cc

Index: cc/animation/animation_host.cc
diff --git a/cc/animation/animation_host.cc b/cc/animation/animation_host.cc
index d61b510f8ea0fe82ca03a3361a7d494d35d69385..ff9af04edd97ad7b69b05833c0af0f2a0c0694d8 100644
--- a/cc/animation/animation_host.cc
+++ b/cc/animation/animation_host.cc
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 
+#include "base/metrics/histogram.h"
 #include "cc/animation/animation_delegate.h"
 #include "cc/animation/animation_id_provider.h"
 #include "cc/animation/animation_player.h"
@@ -217,6 +218,18 @@ void AnimationHost::SetNeedsCommit() {
   layer_tree_mutators_client_->SetMutatorsNeedCommit();
 }
 
+void AnimationHost::ReportAndClearStatsOnFrameEnd() {
+  if (is_impl_instance_)
+    LOCAL_HISTOGRAM_CUSTOM_COUNTS(
+        "Mutators.FindPlayerForLayerImplId",
+        find_player_for_layer_id_stats_.InMicroseconds(), 1, 1000, 10);
+  else
+    LOCAL_HISTOGRAM_CUSTOM_COUNTS(
+        "Mutators.FindPlayerForLayerId",
+        find_player_for_layer_id_stats_.InMicroseconds(), 1, 1000, 10);
+  find_player_for_layer_id_stats_ = base::TimeDelta();
+}
+
 void AnimationHost::PushPropertiesTo(AnimationHost* host_impl) {
   PushTimelinesToImplThread(host_impl);
   RemoveTimelinesFromImplThread(host_impl);
@@ -260,7 +273,9 @@ void AnimationHost::PushPropertiesToImplThread(AnimationHost* host_impl) {
 
 AnimationPlayer* AnimationHost::GetPlayerForLayerId(int layer_id) const {
   DCHECK(layer_id);
+  base::TimeTicks start_time = base::TimeTicks::Now();
   auto iter = layer_to_player_map_.find(layer_id);
+  find_player_for_layer_id_stats_ += base::TimeTicks::Now() - start_time;
   return iter == layer_to_player_map_.end() ? nullptr : iter->second;
 }