Updates the shelf reference before handling display metrics change.

ash/system/web_notification/ash_popup_alignment_delegate.cc

 // 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.
 
 #include "ash/system/web_notification/ash_popup_alignment_delegate.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/shelf/shelf_constants.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_types.h"
@@ skipping 152 matching lines @@
     const gfx::Display& new_display) {
 }
 
 void AshPopupAlignmentDelegate::OnDisplayRemoved(
     const gfx::Display& old_display) {
 }
 
 void AshPopupAlignmentDelegate::OnDisplayMetricsChanged(
     const gfx::Display& display,
     uint32_t metrics) {
+  UpdateShelf();
   if (display.id() == display_id_ && shelf_)
     OnAutoHideStateChanged(shelf_->auto_hide_state());
 }
 
 }  // namespace ash