Remove "top_down" flag in the message center code

ui/message_center/views/message_center_bubble.cc

Index: ui/message_center/views/message_center_bubble.cc
diff --git a/ui/message_center/views/message_center_bubble.cc b/ui/message_center/views/message_center_bubble.cc
index c135b2178a872855a18f096db99fec54fa13aabc..e340ca3f840f5e1e225aefefae0ccef5e6a662be 100644
--- a/ui/message_center/views/message_center_bubble.cc
+++ b/ui/message_center/views/message_center_bubble.cc
@@ -95,9 +95,7 @@ void MessageCenterBubble::InitializeContents(
   set_bubble_view(new_bubble_view);
   bubble_view()->GetWidget()->AddObserver(this);
   message_center_view_ = new MessageCenterView(
-      message_center(), tray(), max_height(), initially_settings_visible_,
-      false); /* MessageCenterBubble should be used only on ChromeOS.
-                 Message center is never shown top down in ChromeOS. */
+      message_center(), tray(), max_height(), initially_settings_visible_);
   bubble_view()->AddChildView(new ContentsView(this, message_center_view_));
   // Resize the content of the bubble view to the given bubble size. This is
   // necessary in case of the bubble border forcing a bigger size then the