Fix ARC notification crash.

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 "ash/wm/window_util.h"
 #include "base/auto_reset.h"
 #include "base/memory/ptr_util.h"
 #include "components/exo/notification_surface.h"
@@ skipping 92 matching lines @@
 
   ArcCustomNotificationView* const owner_;
 
   DISALLOW_COPY_AND_ASSIGN(EventForwarder);
 };
 
 class ArcCustomNotificationView::SlideHelper
     : public ui::LayerAnimationObserver {
  public:
   explicit SlideHelper(ArcCustomNotificationView* owner) : owner_(owner) {
-    owner_->parent()->layer()->GetAnimator()->AddObserver(this);
+    GetSlideOutLayer()->GetAnimator()->AddObserver(this);
 
     // Reset opacity to 1 to handle to case when the surface is sliding before
     // getting managed by this class, e.g. sliding in a popup before showing
     // in a message center view.
     if (owner_->surface_ && owner_->surface_->window())
       owner_->surface_->window()->layer()->SetOpacity(1.0f);
   }
   ~SlideHelper() override {
-    owner_->parent()->layer()->GetAnimator()->RemoveObserver(this);
+    GetSlideOutLayer()->GetAnimator()->RemoveObserver(this);
   }
 
   void Update() {
     const bool has_animation =
-        owner_->parent()->layer()->GetAnimator()->is_animating();
-    const bool has_transform = !owner_->parent()->GetTransform().IsIdentity();
+        GetSlideOutLayer()->GetAnimator()->is_animating();
+    const bool has_transform = !GetSlideOutLayer()->transform().IsIdentity();
     const bool sliding = has_transform || has_animation;
     if (sliding_ == sliding)
       return;
 
     sliding_ = sliding;
 
     if (sliding_)
       OnSlideStart();
     else
       OnSlideEnd();
   }
 
  private:
+  // This is a temporary hack to address crbug.com/718965
+  ui::Layer* GetSlideOutLayer() {
+    ui::Layer* layer = owner_->parent()->layer();
+    return layer ? layer : owner_->GetWidget()->GetLayer();
+  }
+
   void OnSlideStart() {
     if (!owner_->surface_ || !owner_->surface_->window())
       return;
     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);
   }
 
@@ skipping 568 matching lines @@
     }
     if (close_button_) {
       close_button_->set_background(
           views::Background::CreateSolidBackground(current_color));
       close_button_->SchedulePaint();
     }
   }
 }
 
 }  // namespace arc