Moves maintaining ShellObservers back to Shell

ash/common/shelf/shelf_layout_manager.cc

 // Copyright (c) 2012 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/common/shelf/shelf_layout_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <vector>
 
@@ skipping 138 matching lines @@
       mouse_over_shelf_when_auto_hide_timer_started_(false),
       gesture_drag_status_(GESTURE_DRAG_NONE),
       gesture_drag_amount_(0.f),
       gesture_drag_auto_hide_state_(SHELF_AUTO_HIDE_SHOWN),
       update_shelf_observer_(NULL),
       chromevox_panel_height_(0),
       duration_override_in_ms_(0),
       shelf_background_type_(SHELF_BACKGROUND_OVERLAP) {
   DCHECK(shelf_widget_);
   DCHECK(wm_shelf_);
-  WmShell::Get()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
   WmShell::Get()->AddLockStateObserver(this);
   Shell::GetInstance()->activation_client()->AddObserver(this);
   WmShell::Get()->session_controller()->AddSessionStateObserver(this);
   state_.session_state =
       WmShell::Get()->session_controller()->GetSessionState();
 }
 
 ShelfLayoutManager::~ShelfLayoutManager() {
   if (update_shelf_observer_)
     update_shelf_observer_->Detach();
 
   for (auto& observer : observers_)
     observer.WillDeleteShelfLayoutManager();
-  WmShell::Get()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
   WmShell::Get()->RemoveLockStateObserver(this);
   WmShell::Get()->session_controller()->RemoveSessionStateObserver(this);
 }
 
 void ShelfLayoutManager::PrepareForShutdown() {
   in_shutdown_ = true;
   // Stop observing changes to avoid updating a partially destructed shelf.
   Shell::GetInstance()->activation_client()->RemoveObserver(this);
 }
 
@@ skipping 953 matching lines @@
   gesture_drag_status_ = GESTURE_DRAG_NONE;
 }
 
 void ShelfLayoutManager::CancelGestureDrag() {
   gesture_drag_status_ = GESTURE_DRAG_CANCEL_IN_PROGRESS;
   UpdateVisibilityState();
   gesture_drag_status_ = GESTURE_DRAG_NONE;
 }
 
 }  // namespace ash