Deleted AppListViewDelegateObserver class (was unused).

ui/app_list/app_list_view_delegate_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 UI_APP_LIST_APP_LIST_VIEW_DELEGATE_OBSERVER_H_
-#define UI_APP_LIST_APP_LIST_VIEW_DELEGATE_OBSERVER_H_
-
-#include "ui/app_list/app_list_export.h"
-
-namespace app_list {
-
-// TODO(mgiuca): Remove this class; it isn't used any more.
-class APP_LIST_EXPORT AppListViewDelegateObserver {
- public:
-  // Invoked on Chrome shutdown. This is only needed on Mac, since reference-
-  // counting in Objective-C means that simply closing the window isn't enough
-  // to guarantee references to Chrome objects are gone.
-  virtual void OnShutdown() = 0;
-
- protected:
-  virtual ~AppListViewDelegateObserver() {}
-};
-
-}  // namespace app_list
-
-#endif  // UI_APP_LIST_APP_LIST_VIEW_DELEGATE_OBSERVER_H_