Moves maintaining ShellObservers back to Shell

ash/common/wm/dock/docked_window_layout_manager.cc

 // Copyright (c) 2013 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/wm/dock/docked_window_layout_manager.h"
 
 #include "ash/animation/animation_change_type.h"
 #include "ash/common/shelf/shelf_background_animator.h"
 #include "ash/common/shelf/shelf_background_animator_observer.h"
 #include "ash/common/shelf/shelf_constants.h"
@@ skipping 364 matching lines @@
                      wm::WORKSPACE_WINDOW_STATE_FULL_SCREEN),
       docked_width_(0),
       in_overview_(false),
       alignment_(DOCKED_ALIGNMENT_NONE),
       preferred_alignment_(DOCKED_ALIGNMENT_NONE),
       event_source_(DOCKED_ACTION_SOURCE_UNKNOWN),
       last_active_window_(nullptr),
       last_action_time_(base::Time::Now()),
       background_widget_(nullptr) {
   DCHECK(dock_container);
-  dock_container_->GetShell()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
   Shell::GetInstance()->activation_client()->AddObserver(this);
   display::Screen::GetScreen()->AddObserver(this);
 }
 
 DockedWindowLayoutManager::~DockedWindowLayoutManager() {
   Shutdown();
 }
 
 // static
 DockedWindowLayoutManager* DockedWindowLayoutManager::Get(WmWindow* window) {
   if (!window)
     return nullptr;
 
   WmWindow* root = window->GetRootWindow();
   return static_cast<DockedWindowLayoutManager*>(
       root->GetChildByShellWindowId(kShellWindowId_DockedContainer)
           ->GetLayoutManager());
 }
 
 void DockedWindowLayoutManager::Shutdown() {
   background_widget_.reset();
   shelf_observer_.reset();
   shelf_ = nullptr;
   for (WmWindow* child : dock_container_->GetChildren()) {
     child->aura_window()->RemoveObserver(this);
     child->GetWindowState()->RemoveObserver(this);
   }
   Shell::GetInstance()->activation_client()->RemoveObserver(this);
-  dock_container_->GetShell()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
   display::Screen::GetScreen()->RemoveObserver(this);
 }
 
 void DockedWindowLayoutManager::AddObserver(
     DockedWindowLayoutManagerObserver* observer) {
   observer_list_.AddObserver(observer);
 }
 
 void DockedWindowLayoutManager::RemoveObserver(
     DockedWindowLayoutManagerObserver* observer) {
@@ skipping 907 matching lines @@
     const gfx::Rect& keyboard_bounds) {
   // This bounds change will have caused a change to the Shelf which does not
   // propagate automatically to this class, so manually recalculate bounds.
   Relayout();
   UpdateDockBounds(DockedWindowLayoutManagerObserver::KEYBOARD_BOUNDS_CHANGING);
 }
 
 void DockedWindowLayoutManager::OnKeyboardClosed() {}
 
 }  // namespace ash