Refactor accessible focus ring code so the layers are animation observers.

chrome/browser/chromeos/ui/focus_ring_layer.h

 // Copyright 2013 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 CHROME_BROWSER_CHROMEOS_UI_FOCUS_RING_LAYER_H_
 #define CHROME_BROWSER_CHROMEOS_UI_FOCUS_RING_LAYER_H_
 
 #include <memory>
 
 #include "base/macros.h"
+#include "base/time/time.h"
+#include "ui/compositor/compositor_animation_observer.h"
 #include "ui/compositor/layer_delegate.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ui {
+class Compositor;
 class Layer;
 }
 
 namespace chromeos {
 
 // A delegate interface implemented by the object that owns a FocusRingLayer.
 class FocusRingLayerDelegate {
  public:
   virtual void OnDeviceScaleFactorChanged() = 0;
+  virtual void OnAnimationStep(base::TimeTicks timestamp) = 0;
 
  protected:
   virtual ~FocusRingLayerDelegate();
 };
 
 // FocusRingLayer draws a focus ring at a given global rectangle.
-class FocusRingLayer : public ui::LayerDelegate {
+class FocusRingLayer : public ui::LayerDelegate,
+                       public ui::CompositorAnimationObserver {
  public:
   explicit FocusRingLayer(FocusRingLayerDelegate* delegate);
   ~FocusRingLayer() override;
 
   // Move the focus ring layer to the given bounds in the coordinates of
   // the given root window.
   void Set(aura::Window* root_window, const gfx::Rect& bounds);
 
+  // Returns true if this layer is in a composited window with an
+  // animation observer.
+  bool CanAnimate() const;
+
   ui::Layer* layer() { return layer_.get(); }
   aura::Window* root_window() { return root_window_; }
 
  protected:
   // Updates |root_window_| and creates |layer_| if it doesn't exist,
   // or if the root window has changed. Moves the layer to the top if
   // it wasn't there already.
-  void CreateOrUpdateLayer(aura::Window* root_window, const char* layer_name);
+  void CreateOrUpdateLayer(aura::Window* root_window,
+                           const char* layer_name,
+                           const gfx::Rect& bounds);
 
  private:
   // ui::LayerDelegate overrides:
   void OnPaintLayer(const ui::PaintContext& context) override;
   void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override;
   void OnDeviceScaleFactorChanged(float device_scale_factor) override;
   base::Closure PrepareForLayerBoundsChange() override;
 
+  // CompositorAnimationObserver overrides:
+  void OnAnimationStep(base::TimeTicks timestamp) override;
+  void OnCompositingShuttingDown(ui::Compositor* compositor) override;
+
   // The object that owns this layer.
   FocusRingLayerDelegate* delegate_;
 
   // The current root window containing the focused object.
   aura::Window* root_window_;
 
   // The current layer.
   std::unique_ptr<ui::Layer> layer_;
 
   // The bounding rectangle of the focused object, in |root_window_|
   // coordinates.
   gfx::Rect focus_ring_;
 
+  // The compositor associated with this layer.
+  ui::Compositor* compositor_;
+
   DISALLOW_COPY_AND_ASSIGN(FocusRingLayer);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_UI_FOCUS_RING_LAYER_H_