Moved some message center constants to message_center_constants.h.

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 b7a6390c7f7f7add2356bd7cbd7e2af4826bccc8..c5e9308ea2378c5e3f18b54cc80251d3eb360ebd 100644
--- a/ui/message_center/views/message_center_view.cc
+++ b/ui/message_center/views/message_center_view.cc
@@ -392,10 +392,8 @@ void MessageCenterView::SetNotifications(
   for (NotificationList::Notifications::const_iterator iter =
            notifications.begin(); iter != notifications.end(); ++iter) {
     AddNotification(*(*iter));
-    if (message_views_.size() >=
-        NotificationList::kMaxVisibleMessageCenterNotifications) {
+    if (message_views_.size() >= kMaxVisibleMessageCenterNotifications)
       break;
-    }
   }
   if (message_views_.empty()) {
     views::Label* label = new views::Label(l10n_util::GetStringUTF16(