Generalize layer mirroring for phantom windows

ui/arc/notification/arc_custom_notification_view.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 "ui/arc/notification/arc_custom_notification_view.h"
 
 #include "base/auto_reset.h"
 #include "components/exo/notification_surface.h"
 #include "components/exo/surface.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ skipping 95 matching lines @@
     if (sliding_)
       OnSlideStart();
     else
       OnSlideEnd();
   }
 
  private:
   void OnSlideStart() {
     if (!owner_->surface_ || !owner_->surface_->window())
       return;
-    surface_copy_ = ::wm::RecreateLayers(owner_->surface_->window(), nullptr);
+    surface_copy_ = ::wm::RecreateLayers(owner_->surface_->window());
     // |surface_copy_| is at (0, 0) in owner_->layer().
     surface_copy_->root()->SetBounds(gfx::Rect(surface_copy_->root()->size()));
     owner_->layer()->Add(surface_copy_->root());
     owner_->surface_->window()->layer()->SetOpacity(0.0f);
   }
 
   void OnSlideEnd() {
     if (!owner_->surface_ || !owner_->surface_->window())
       return;
     owner_->surface_->window()->layer()->SetOpacity(1.0f);
@@ skipping 316 matching lines @@
 
 void ArcCustomNotificationView::OnNotificationSurfaceRemoved(
     exo::NotificationSurface* surface) {
   if (surface->notification_id() != notification_key_)
     return;
 
   SetSurface(nullptr);
 }
 
 }  // namespace arc