tweak the focus rectangle of TrayBackgroundView objects

ash/common/system/tray/actionable_view.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 ASH_COMMON_SYSTEM_TRAY_ACTIONABLE_VIEW_H_
 #define ASH_COMMON_SYSTEM_TRAY_ACTIONABLE_VIEW_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/system/tray/tray_popup_ink_drop_style.h"
 #include "base/macros.h"
@@ skipping 25 matching lines @@
 
   void SetAccessibleName(const base::string16& name);
   const base::string16& accessible_name() const { return accessible_name_; }
 
   // Closes the system tray bubble. The |owner_| must not be nullptr.
   void CloseSystemBubble();
 
  protected:
   SystemTrayItem* owner() { return owner_; }
 
-  void OnPaintFocus(gfx::Canvas* canvas);
+  // Draws focus rectangle on the canvas.
+  // Default implementation draws the focus rectangle with certain inset and
+  // color. Subclasses can override to change the default settings.
+  virtual void OnPaintFocus(gfx::Canvas* canvas);
 
   // Returns the bounds to paint the focus rectangle in.
   virtual gfx::Rect GetFocusBounds();
 
   // Performs an action when user clicks on the view (on mouse-press event), or
   // presses a key when this view is in focus. Returns true if the event has
   // been handled and an action was performed. Returns false otherwise.
   virtual bool PerformAction(const ui::Event& event) = 0;
 
   // Called after PerformAction() to act upon its result, including showing
@@ skipping 49 matching lines @@
 
  private:
   views::ButtonListener* listener_;
 
   DISALLOW_COPY_AND_ASSIGN(ButtonListenerActionableView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_ACTIONABLE_VIEW_H_