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

chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc

 // Copyright 2016 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/accessibility_cursor_ring_layer.h"
 
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "third_party/skia/include/core/SkPaint.h"
@@ skipping 32 matching lines @@
 
   gfx::Rect bounds = gfx::Rect(location.x(), location.y(), 0, 0);
   int inset = kGradientWidth + kCursorRingRadius + kLayerMargin;
   bounds.Inset(-inset, -inset, -inset, -inset);
 
   display::Display display =
       display::Screen::GetScreen()->GetDisplayMatching(bounds);
   aura::Window* root_window = ash::Shell::GetInstance()
                                   ->window_tree_host_manager()
                                   ->GetRootWindowForDisplayId(display.id());
-  CreateOrUpdateLayer(root_window, "AccessibilityCursorRing");
-
-  // Update the layer bounds.
-  layer()->SetBounds(bounds);
+  CreateOrUpdateLayer(root_window, "AccessibilityCursorRing", bounds);
 }
 
 void AccessibilityCursorRingLayer::SetOpacity(float opacity) {
   layer()->SetOpacity(opacity);
 }
 
 void AccessibilityCursorRingLayer::OnPaintLayer(
     const ui::PaintContext& context) {
   ui::PaintRecorder recorder(context, layer()->size());
 
@@ skipping 10 matching lines @@
     paint.setColor(
         SkColorSetARGBMacro(255 * (i) * (i) / (w * w), red_, green_, blue_));
     SkPath path;
     path.addOval(SkRect::MakeXYWH(r.x(), r.y(), r.width(), r.height()));
     r.Inset(1, 1, 1, 1);
     recorder.canvas()->DrawPath(path, paint);
   }
 }
 
 }  // namespace chromeos