mash: Move WmShelfAura ownership to RootWindowController and init it earlier

ash/common/wm/workspace/workspace_layout_manager_delegate.h

 // 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_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_DELEGATE_H_
 #define ASH_COMMON_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_DELEGATE_H_
 
 #include "ash/ash_export.h"
 
 namespace ash {
 namespace wm {
 
 class ASH_EXPORT WorkspaceLayoutManagerDelegate {
  public:
   virtual ~WorkspaceLayoutManagerDelegate() {}
 
   // Called when the visibility of the shelf needs to be updated.
+  // TODO(jamescook): Eliminate this and use WmShelf directly.
   virtual void UpdateShelfVisibility() = 0;
 
   // Called when the fullscreen state has changed to |is_fullscreen|.
   virtual void OnFullscreenStateChanged(bool is_fullscreen) = 0;
 };
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_DELEGATE_H_