Transfer responsibility for providing a close button for a notification to each implementation of M…

ui/message_center/views/custom_notification_view.h

Index: ui/message_center/views/custom_notification_view.h
diff --git a/ui/message_center/views/custom_notification_view.h b/ui/message_center/views/custom_notification_view.h
index 8a5ab622deea929da6d603909f4e6292f07c5823..6a7a2a2d43f2e06bde516a3fb79bd4c18f9c6749 100644
--- a/ui/message_center/views/custom_notification_view.h
+++ b/ui/message_center/views/custom_notification_view.h
@@ -21,6 +21,9 @@ class MESSAGE_CENTER_EXPORT CustomNotificationView : public MessageView {
 
   // Overidden from MessageView:
   void SetDrawBackgroundAsActive(bool active) override;
+  bool IsCloseButtonFocused() const override;
+  void RequestFocusOnCloseButton() override;
+  bool IsPinned() const override;
 
   // Overridden from views::View:
   gfx::Size GetPreferredSize() const override;
@@ -31,6 +34,8 @@ class MESSAGE_CENTER_EXPORT CustomNotificationView : public MessageView {
 
   // The view for the custom content. Owned by view hierarchy.
   views::View* contents_view_ = nullptr;
+  std::unique_ptr<CustomNotificationContentViewDelegate>
+      contents_view_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(CustomNotificationView);
 };