Moves maintaining ShellObservers back to Shell

ash/common/shelf/wm_shelf.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/common/shelf/wm_shelf.h"
 
 #include "ash/common/shelf/shelf_controller.h"
 #include "ash/common/shelf/shelf_delegate.h"
 #include "ash/common/shelf/shelf_item_delegate.h"
 #include "ash/common/shelf/shelf_layout_manager.h"
@@ skipping 150 matching lines @@
       alignment != SHELF_ALIGNMENT_BOTTOM_LOCKED) {
     shelf_locking_manager_->set_stored_alignment(alignment);
     return;
   }
 
   alignment_ = alignment;
   // The ShelfWidget notifies the ShelfView of the alignment change.
   shelf_widget_->OnShelfAlignmentChanged();
   shelf_layout_manager_->LayoutShelf();
   WmShell::Get()->shelf_controller()->NotifyShelfAlignmentChanged(this);
-  WmShell::Get()->NotifyShelfAlignmentChanged(GetWindow()->GetRootWindow());
+  Shell::GetInstance()->NotifyShelfAlignmentChanged(
+      GetWindow()->GetRootWindow());
 }
 
 bool WmShelf::IsHorizontalAlignment() const {
   switch (alignment_) {
     case SHELF_ALIGNMENT_BOTTOM:
     case SHELF_ALIGNMENT_BOTTOM_LOCKED:
       return true;
     case SHELF_ALIGNMENT_LEFT:
     case SHELF_ALIGNMENT_RIGHT:
       return false;
@@ skipping 23 matching lines @@
 }
 
 void WmShelf::SetAutoHideBehavior(ShelfAutoHideBehavior auto_hide_behavior) {
   DCHECK(shelf_layout_manager_);
 
   if (auto_hide_behavior_ == auto_hide_behavior)
     return;
 
   auto_hide_behavior_ = auto_hide_behavior;
   WmShell::Get()->shelf_controller()->NotifyShelfAutoHideBehaviorChanged(this);
-  WmShell::Get()->NotifyShelfAutoHideBehaviorChanged(
+  Shell::GetInstance()->NotifyShelfAutoHideBehaviorChanged(
       GetWindow()->GetRootWindow());
 }
 
 ShelfAutoHideState WmShelf::GetAutoHideState() const {
   return shelf_layout_manager_->auto_hide_state();
 }
 
 void WmShelf::UpdateAutoHideState() {
   shelf_layout_manager_->UpdateAutoHideState();
 }
@@ skipping 140 matching lines @@
 
 void WmShelf::OnBackgroundUpdated(ShelfBackgroundType background_type,
                                   AnimationChangeType change_type) {
   if (background_type == GetBackgroundType())
     return;
   for (auto& observer : observers_)
     observer.OnBackgroundTypeChanged(background_type, change_type);
 }
 
 }  // namespace ash