Make message center always scroll up upon notification removal

ui/message_center/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 
 component("message_center") {
   defines = [ "MESSAGE_CENTER_IMPLEMENTATION" ]
 
@@ skipping 36 matching lines @@
       "notification_delegate.h",
       "message_center_impl.cc",
       "message_center_impl.h",
       "message_center_observer.h",
       "message_center_style.cc",
       "message_center_style.h",
       "message_center_tray.cc",
       "message_center_tray.h",
       "message_center_tray_delegate.h",
       "message_center_types.h",
+      "message_center_switches.h",
+      "message_center_switches.cc",
       "notification.cc",
       "notification.h",
       "notification_blocker.cc",
       "notification_blocker.h",
       "notification_list.cc",
       "notification_list.h",
       "notification_types.cc",
       "notification_types.h",
       "notifier_settings.cc",
       "notifier_settings.h",
@@ skipping 146 matching lines @@
       deps += [
         # Compositor is needed by message_center_view_unittest.cc and for the
         # fonts used by bounded_label_unittest.cc.
         "//ui/compositor",
         "//ui/views",
         "//ui/views:test_support",
       ]
     }
   }  # enable_notifications
 }