Introduce AccessibilityFocusRing.

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 "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/compositor/layer_delegate.h"
@@ skipping 21 matching lines @@
 // FocusRingLayer draws a focus ring at a given global rectangle.
 class FocusRingLayer : public ui::LayerDelegate {
  public:
   explicit FocusRingLayer(FocusRingLayerDelegate* delegate);
   virtual ~FocusRingLayer();
 
   // 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);
 
+ 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);
+
+  // The current root window containing the focused object.
+  aura::Window* root_window_;

[xiyuan, 2014/09/11 21:56:05]

nit: Can we keep the members in private section and provide an accessors
instead?

[dmazzoni, 2014/09/11 22:14:39]

Done.

+
+  // The current layer.
+  scoped_ptr<ui::Layer> layer_;
+
  private:
   // ui::LayerDelegate overrides:
   virtual void OnPaintLayer(gfx::Canvas* canvas) OVERRIDE;
   virtual void OnDelegatedFrameDamage(
       const gfx::Rect& damage_rect_in_dip) OVERRIDE;
   virtual void OnDeviceScaleFactorChanged(float device_scale_factor) OVERRIDE;
   virtual base::Closure PrepareForLayerBoundsChange() OVERRIDE;
 
   // The object that owns this layer.
   FocusRingLayerDelegate* delegate_;
 
-  // The current root window containing the focused object.
-  aura::Window* root_window_;
-
   // The bounding rectangle of the focused object, in |root_window_|
   // coordinates.
   gfx::Rect focus_ring_;
 
-  // The current layer.
-  scoped_ptr<ui::Layer> layer_;
-
   DISALLOW_COPY_AND_ASSIGN(FocusRingLayer);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_UI_FOCUS_RING_LAYER_H_