Make message center always scroll up upon notification removal

ui/message_center/message_center_switches.h

+// 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.
+
+#ifndef UI_MESSAGE_CENTER_MESSAGE_CENTER_SWITCHES_H_
+#define UI_MESSAGE_CENTER_MESSAGE_CENTER_SWITCHES_H_
+
+#include "base/compiler_specific.h"
+#include "ui/message_center/message_center_export.h"
+
+namespace switches {
+
+MESSAGE_CENTER_EXPORT extern const char
+    kEnableMessageCenterAlwaysScrollUpUponNotificationRemoval[];
+
+}  // namespace switches
+
+#endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_SWITCHES_H_