views: Convert IsFocusable() to just focusable() since it's just a simple accessor.

ui/views/controls/button/custom_button.cc

 // Copyright (c) 2011 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 "ui/views/controls/button/custom_button.h"
 
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/base/animation/throb_animation.h"
 #include "ui/base/keycodes/keyboard_codes.h"
 #include "ui/gfx/screen.h"
@@ skipping 261 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // CustomButton, View overrides (protected):
 
 void CustomButton::ViewHierarchyChanged(bool is_add, View *parent,
                                         View *child) {
   if (!is_add && state_ != BS_DISABLED)
     SetState(BS_NORMAL);
 }
 
-bool CustomButton::IsFocusable() const {
-  return (state_ != BS_DISABLED) && View::IsFocusable();
-}
-
 void CustomButton::OnBlur() {
   if (IsHotTracked())
     SetState(BS_NORMAL);
 }
 
 }  // namespace views