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

chrome/browser/chromeos/ui/focus_ring_controller.cc

 // 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.
 
 #include "chrome/browser/chromeos/ui/focus_ring_controller.h"
 
 #include "ash/system/tray/actionable_view.h"
 #include "ash/system/tray/tray_background_view.h"
 #include "ash/system/tray/tray_popup_header_button.h"
 #include "ash/wm/window_util.h"
@@ skipping 80 matching lines @@
   // Update the focus ring layer.
   if (!focus_ring_layer_)
     focus_ring_layer_.reset(new FocusRingLayer(this));
   focus_ring_layer_->Set(root_window, view_bounds);
 }
 
 void FocusRingController::OnDeviceScaleFactorChanged() {
   UpdateFocusRing();
 }
 
+void FocusRingController::OnAnimationStep(base::TimeTicks timestamp) {}
+
 void FocusRingController::SetWidget(views::Widget* widget) {
   if (widget_) {
     widget_->RemoveObserver(this);
     if (widget_->GetFocusManager())
       widget_->GetFocusManager()->RemoveFocusChangeListener(this);
   }
 
   widget_ = widget;
 
   if (widget_) {
@@ skipping 26 matching lines @@
                                             views::View* focused_now) {
 }
 
 void FocusRingController::OnDidChangeFocus(views::View* focused_before,
                                            views::View* focused_now) {
   DCHECK_EQ(focused_now, widget_->GetFocusManager()->GetFocusedView());
   UpdateFocusRing();
 }
 
 }  // namespace chromeos