Moves maintaining ShellObservers back to Shell

ash/aura/wm_shell_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_shell_aura.h"
 
 #include <utility>
 
 #include "ash/aura/key_event_watcher_aura.h"
 #include "ash/aura/pointer_watcher_adapter.h"
@@ skipping 206 matching lines @@
 
 std::unique_ptr<ImmersiveFullscreenController>
 WmShellAura::CreateImmersiveFullscreenController() {
   return base::MakeUnique<ImmersiveFullscreenController>();
 }
 
 std::unique_ptr<KeyEventWatcher> WmShellAura::CreateKeyEventWatcher() {
   return base::MakeUnique<KeyEventWatcherAura>();
 }
 
-void WmShellAura::OnOverviewModeStarting() {
-  for (auto& observer : *shell_observers())
-    observer.OnOverviewModeStarting();
-}
-
-void WmShellAura::OnOverviewModeEnded() {
-  for (auto& observer : *shell_observers())
-    observer.OnOverviewModeEnded();
-}
-
 SessionStateDelegate* WmShellAura::GetSessionStateDelegate() {
   return Shell::GetInstance()->session_state_delegate();
 }
 
 void WmShellAura::AddDisplayObserver(WmDisplayObserver* observer) {
   if (!added_display_observer_) {
     added_display_observer_ = true;
     Shell::GetInstance()->window_tree_host_manager()->AddObserver(this);
   }
   display_observers_.AddObserver(observer);
@@ skipping 58 matching lines @@
   for (auto& observer : display_observers_)
     observer.OnDisplayConfigurationChanging();
 }
 
 void WmShellAura::OnDisplayConfigurationChanged() {
   for (auto& observer : display_observers_)
     observer.OnDisplayConfigurationChanged();
 }
 
 }  // namespace ash