Introduces a new scrollbar for message_center.

ui/message_center/views/message_center_view.cc

Index: ui/message_center/views/message_center_view.cc
diff --git a/ui/message_center/views/message_center_view.cc b/ui/message_center/views/message_center_view.cc
index 4c20b715ac0eca84f40f21f399cd18e21f2a6993..589d4980369e94c3230e808631c41367df0ef997 100644
--- a/ui/message_center/views/message_center_view.cc
+++ b/ui/message_center/views/message_center_view.cc
@@ -31,7 +31,7 @@
 #include "ui/views/controls/button/label_button.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/scroll_view.h"
-#include "ui/views/controls/scrollbar/kennedy_scroll_bar.h"
+#include "ui/views/controls/scrollbar/overlay_scroll_bar.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/grid_layout.h"
 #include "ui/views/painter.h"
@@ -306,7 +306,7 @@ BoundedScrollView::BoundedScrollView(int min_height, int max_height)
   if (IsRichNotificationEnabled()) {
     set_background(views::Background::CreateSolidBackground(
         kMessageCenterBackgroundColor));
-    SetVerticalScrollBar(new views::KennedyScrollBar(false));
+    SetVerticalScrollBar(new views::OverlayScrollBar(false));
   }
 }