mash: Remove WmRootWindowControllerObserver.

ash/common/wm_root_window_controller_observer.h

Index: ash/common/wm_root_window_controller_observer.h
diff --git a/ash/common/wm_root_window_controller_observer.h b/ash/common/wm_root_window_controller_observer.h
deleted file mode 100644
index dd959f1ad28984339248b172a9665a1c2c03d0f9..0000000000000000000000000000000000000000
--- a/ash/common/wm_root_window_controller_observer.h
+++ /dev/null
@@ -1,26 +0,0 @@
-// Copyright 2016 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_COMMON_WM_ROOT_WINDOW_CONTROLLER_OBSERVER_H_
-#define ASH_COMMON_WM_ROOT_WINDOW_CONTROLLER_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace ash {
-
-class WmWindow;
-
-// TODO(sky): nuke and go back to ShellObserver.
-class ASH_EXPORT WmRootWindowControllerObserver {
- public:
-  virtual void OnWorkAreaChanged() {}
-  virtual void OnShelfAlignmentChanged() {}
-
- protected:
-  virtual ~WmRootWindowControllerObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_WM_ROOT_WINDOW_CONTROLLER_OBSERVER_H_