[animations] Adds metrics for jank on selected layer animations

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 7ecc5e588db8b8c2d1d7f82fb0b3f1c9618703b9..6bf491ee976a139280893e07221f4bcf1a2287a3 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -390,6 +390,7 @@ class COMPOSITOR_EXPORT Compositor
   }
 
   const cc::FrameSinkId& frame_sink_id() const { return frame_sink_id_; }
+  int submitted_frame_number() const { return submitted_frame_number_; }
 
  private:
   friend class base::RefCounted<Compositor>;
@@ -416,6 +417,8 @@ class COMPOSITOR_EXPORT Compositor
 #if defined(USE_AURA)
   ui::Window* window_;
 #endif
+  // A sequence number of a current compositor frame for use with metrics.
+  int submitted_frame_number_;
   // A map from child id to parent id.
   std::unordered_set<cc::FrameSinkId, cc::FrameSinkIdHash> child_frame_sinks_;
   bool widget_valid_;