React to primary display change instead of removal

chrome/browser/chromeos/login/ui/login_display_host_impl.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 99 matching lines @@
   void RenderProcessGone(base::TerminationStatus status) override;
 
   // Overridden from chromeos::SessionManagerClient::Observer:
   void EmitLoginPromptVisibleCalled() override;
 
   // Overridden from chromeos::CrasAudioHandler::AudioObserver:
   void OnActiveOutputNodeChanged() override;
 
   // Overridden from display::DisplayObserver:
   void OnDisplayAdded(const display::Display& new_display) override;
-  void OnDisplayRemoved(const display::Display& old_display) override;
   void OnDisplayMetricsChanged(const display::Display& display,
                                uint32_t changed_metrics) override;
 
   // Overriden from views::WidgetRemovalsObserver:
   void OnWillRemoveView(views::Widget* widget, views::View* view) override;
 
   // Overriden from chrome::MultiUserWindowManager::Observer:
   void OnUserSwitchAnimationFinished() override;
 
  private:
@@ skipping 175 matching lines @@
 
   base::WeakPtrFactory<LoginDisplayHostImpl> pointer_factory_;
   base::WeakPtrFactory<LoginDisplayHostImpl> animation_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LoginDisplayHostImpl);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_