Remove "Alternate frame caption button style" command line flag

ash/frame/caption_buttons/frame_maximize_button_observer.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_FRAME_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_
-#define ASH_FRAME_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace views {
-class Widget;
-}
-
-namespace ash {
-
-class ASH_EXPORT FrameMaximizeButtonObserver {
- public:
-  virtual ~FrameMaximizeButtonObserver() {}
-
-  // Called when the maximize button's help bubble is shown.
-  virtual void OnMaximizeBubbleShown(views::Widget* bubble) = 0;
-};
-
-}  // namespace ash
-
-#endif  // ASH_FRAME_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_