Remove unused class ShellAppWindowController

extensions/shell/browser/shell_app_window_controller.h

-// Copyright 2014 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 EXTENSIONS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_
-#define EXTENSIONS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_
-
-namespace content {
-class BrowserContext;
-}
-
-namespace extensions {
-
-class Extension;
-class ShellAppWindow;
-
-class ShellAppWindowController {
- public:
-  virtual ~ShellAppWindowController() {}
-
-  // Creates a new app window and adds it to the desktop. This class should
-  // maintain the ownership of the window.
-  virtual ShellAppWindow* CreateAppWindow(content::BrowserContext* context,
-                                          const Extension* extension) = 0;
-
-  // Closes and destroys the app windows. Must be called before the extension
-  // is destroyed.
-  virtual void CloseAppWindows() = 0;
-};
-
-}  // namespace extensions
-
-#endif  // EXTENSIONS_SHELL_BROWSER_SHELL_APP_WINDOW_CONTROLLER_H_