Add UpdateNotificationSize to MessageCenterController.

ui/message_center/views/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/message_center/views/custom_notification_view.h"
 
 #include <algorithm>
 
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/ime/text_input_type.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/message_center/message_center_style.h"
+#include "ui/message_center/views/message_center_controller.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/painter.h"
 
 namespace message_center {
 
 CustomNotificationView::CustomNotificationView(
     MessageCenterController* controller,
     const Notification& notification)
@@ skipping 114 matching lines @@
         // back space and return keys. So that these key events are sent to the
         // arc container correctly without being handled by the message center.
         return false;
       }
     }
   }
 
   return MessageView::OnKeyPressed(event);
 }
 
+void CustomNotificationView::ChildPreferredSizeChanged(View* child) {
+  // Notify MessageCenterController when the custom content changes size,
+  // as it may need to relayout.
+  controller()->UpdateNotificationSize(notification_id());
+}
+
 }  // namespace message_center