[animations] Adds metrics for jank on selected layer animations

ui/compositor/compositor.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 373 matching lines @@
   const cc::LayerTreeDebugState& GetLayerTreeDebugState() const;
   void SetLayerTreeDebugState(const cc::LayerTreeDebugState& debug_state);
   const cc::RendererSettings& GetRendererSettings() const;
 
   LayerAnimatorCollection* layer_animator_collection() {
     return &layer_animator_collection_;
   }
 
   const cc::FrameSinkId& frame_sink_id() const { return frame_sink_id_; }
 
+  // Returns a sequence number of a current compositor frame for use with UMA.
+  int GetFrameNumber();
+
  private:
   friend class base::RefCounted<Compositor>;
   friend class CompositorLock;
 
   // Called by CompositorLock.
   void UnlockCompositor();
 
   // Called to release any pending CompositorLock
   void CancelCompositorLock();
 
@@ skipping 39 matching lines @@
   gfx::ColorSpace color_space_;
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_