ash: Move ShelfWidget ownership to WmShelf and refactor access to it

ash/aura/wm_shelf_aura.cc

 // 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.
 
 #include "ash/aura/wm_shelf_aura.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shelf/shelf_layout_manager.h"
 #include "ash/shelf/dimmer_view.h"
 #include "ash/shelf/shelf_bezel_event_handler.h"
@@ skipping 33 matching lines @@
 // WmShelfAura -----------------------------------------------------------------
 
 WmShelfAura::WmShelfAura() {}
 
 WmShelfAura::~WmShelfAura() {}
 
 WmDimmerView* WmShelfAura::CreateDimmerView(bool disable_animations_for_test) {
   return DimmerView::Create(this, disable_animations_for_test);
 }
 
-void WmShelfAura::SetShelfLayoutManager(ShelfLayoutManager* manager) {
-  WmShelf::SetShelfLayoutManager(manager);
+void WmShelfAura::CreateShelfWidget(WmWindow* root) {
+  WmShelf::CreateShelfWidget(root);
   bezel_event_handler_.reset(new ShelfBezelEventHandler(this));
 }
 
 void WmShelfAura::WillDeleteShelfLayoutManager() {
   // Clear event handlers that might forward events to the destroyed instance.
   auto_hide_event_handler_.reset();
   bezel_event_handler_.reset();
   WmShelf::WillDeleteShelfLayoutManager();
 }
 
 void WmShelfAura::WillChangeVisibilityState(ShelfVisibilityState new_state) {
   WmShelf::WillChangeVisibilityState(new_state);
   if (new_state != SHELF_AUTO_HIDE) {
     auto_hide_event_handler_.reset();
   } else if (!auto_hide_event_handler_) {
     auto_hide_event_handler_.reset(
         new AutoHideEventHandler(shelf_layout_manager()));
   }
 }
 
 }  // namespace ash