[animations] Adds metrics for jank on selected layer animations

ui/compositor/layer_animator.cc

Index: ui/compositor/layer_animator.cc
diff --git a/ui/compositor/layer_animator.cc b/ui/compositor/layer_animator.cc
index 141e7dd18bad6b16bfc4f7ad73f66fa8c27c6fa5..e66a3c7c97fac6c3fc9fdd81097a13518da76154 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -53,7 +53,8 @@ LayerAnimator::LayerAnimator(base::TimeDelta transition_duration)
       tween_type_(gfx::Tween::LINEAR),
       is_started_(false),
       disable_timer_for_test_(false),
-      adding_animations_(false) {
+      adding_animations_(false),
+      animation_metrics_reporter_(nullptr) {
   animation_player_ =
       cc::AnimationPlayer::Create(cc::AnimationIdProvider::NextPlayerId());
 }
@@ -97,7 +98,10 @@ LayerAnimator* LayerAnimator::CreateImplicitAnimator() {
     std::unique_ptr<LayerAnimationElement> element =                    \
         LayerAnimationElement::Create##name##Element(value, duration);  \
     element->set_tween_type(tween_type_);                               \
-    StartAnimation(new LayerAnimationSequence(std::move(element)));     \
+    LayerAnimationSequence* sequence =                                  \
+        new LayerAnimationSequence(std::move(element));                 \
+    sequence->SetAnimationMetricsReporter(animation_metrics_reporter_); \
+    StartAnimation(sequence);                                           \

[sadrul, 2017/01/20 17:29:43]

Does this cover all the cases? e.g. what if LayerAnimator::StartTogether() is
called to trigger some animation?

[ajuma, 2017/01/20 23:02:06]

This is a good point, what about moving this logic into StartAnimation (since
that also gets called for StartTogether)?

   }                                                                     \
                                                                         \
   member_type LayerAnimator::GetTarget##name() const {                  \