Remove base/win/metro.{cc|h} and some associated code

chrome/browser/ui/views/frame/browser_frame_ashwin.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_UI_VIEWS_FRAME_BROWSER_FRAME_ASHWIN_H_
-#define CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_ASHWIN_H_
-
-#include "base/macros.h"
-#include "chrome/browser/ui/views/frame/browser_frame_ash.h"
-
-// A NativeWidgetAura subclass that provides Windows-specific behavior on the
-// Ash desktop for Metro mode.
-class BrowserFrameAshWin : public BrowserFrameAsh {
- public:
-  BrowserFrameAshWin(BrowserFrame* browser_frame, BrowserView* browser_view);
-
- protected:
-  ~BrowserFrameAshWin() override;
-
-  // Overridden from aura::client::ActivationChangeObserver:
-  void OnWindowFocused(aura::Window* gained_focus,
-                       aura::Window* lost_focus) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BrowserFrameAshWin);
-};
-
-#endif  // CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_ASHWIN_H_