Fix the typo "visibility".

ui/message_center/views/message_center_button_bar.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 UI_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_BUTTON_BAR_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_BUTTON_BAR_H_
 
 #include "ui/views/controls/button/button.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/view.h"
@@ skipping 28 matching lines @@
   virtual void SetAllButtonsEnabled(bool enabled);
 
   // Sometimes we shouldn't see the close-all button.
   void SetCloseAllButtonEnabled(bool enabled);
 
   // Sometimes we shouldn't see the back arrow (not in settings).
   void SetBackArrowVisible(bool visible);
 
  private:
   // Updates the layout manager which can have differing configuration
-  // depending on the visibilty of different parts of the button bar.
+  // depending on the visibility of different parts of the button bar.
   void ViewVisibilityChanged();
 
   // Overridden from views::View:
   void ChildVisibilityChanged(views::View* child) override;
 
   // Overridden from views::ButtonListener:
   void ButtonPressed(views::Button* sender, const ui::Event& event) override;
 
   MessageCenterView* message_center_view() const {
     return message_center_view_;
@@ skipping 19 matching lines @@
   NotificationCenterButton* close_all_button_;
   NotificationCenterButton* settings_button_;
   NotificationCenterButton* quiet_mode_button_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageCenterButtonBar);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_VIEWS_MESSAGE_CENTER_BUTTON_BAR_H_