Fix the check to distinguish accessibility events.

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 537 matching lines @@
 }
 
 bool ArcCustomNotificationView::OnMousePressed(const ui::MouseEvent& event) {
   // TODO(yhanada): Remove this hack as soon as possible after letting
   // accessible actions be delivered to this view.
   // All mouse clicks or touches should be sent to corresponding Android view
   // because the surface is on this view, so receiving a mouse pressed event
   // means the event is generated by automation API.
   if (event.IsOnlyLeftMouseButton() &&
       item_->expand_state() != mojom::ArcNotificationExpandState::FIXED_SIZE &&
-      event.target() != surface_->window()) {
+      event.target() == nullptr) {

[yoshiki, 2017/04/05 08:55:51]

Could you update the comment above and mention about the logic of the null
check?

     item_->ToggleExpansion();
     return true;
   }
   return false;
 }
 
 void ArcCustomNotificationView::ButtonPressed(views::Button* sender,
                                               const ui::Event& event) {
   if (item_ && !item_->pinned() && sender == close_button_.get()) {
     CHECK_EQ(message_center::CustomNotificationView::kViewClassName,
@@ skipping 45 matching lines @@
 
 void ArcCustomNotificationView::OnNotificationSurfaceRemoved(
     exo::NotificationSurface* surface) {
   if (surface->notification_id() != notification_key_)
     return;
 
   SetSurface(nullptr);
 }
 
 }  // namespace arc