Revert 115515 - [Aura] Implement views-based applist.

ui/aura_shell/app_list/app_list_view_delegate.h

-// 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.
-
-#ifndef UI_AURA_SHELL_APP_LIST_APP_LIST_VIEW_DELEGATE_H_
-#define UI_AURA_SHELL_APP_LIST_APP_LIST_VIEW_DELEGATE_H_
-#pragma once
-
-#include "ui/aura_shell/aura_shell_export.h"
-
-namespace aura_shell {
-
-class AppListItemModel;
-
-class AURA_SHELL_EXPORT AppListViewDelegate {
- public:
-  // AppListView owns the delegate.
-  virtual ~AppListViewDelegate() {}
-
-  // Invoked an AppListeItemModelView is  activated by click or enter key.
-  virtual void OnAppListItemActivated(AppListItemModel* item,
-                                      int event_flags) = 0;
-};
-
-}  // namespace aura_shell
-
-#endif  // UI_AURA_SHELL_APP_LIST_APP_LIST_VIEW_DELEGATE_H_