[Mac] Delete old balloon and Notification Center notification implementations.

ui/message_center/message_center_util.cc

Index: ui/message_center/message_center_util.cc
diff --git a/ui/message_center/message_center_util.cc b/ui/message_center/message_center_util.cc
index c1dc58c3c8aafa0d10829ba93efceabd0a8c4829..f5b3149d61943746294b55bb7c1d258e66d0cec4 100644
--- a/ui/message_center/message_center_util.cc
+++ b/ui/message_center/message_center_util.cc
@@ -13,9 +13,9 @@ namespace message_center {
 // when a time period in Canary indicates the new notifications are acceptable
 // for default behavior.
 bool IsRichNotificationEnabled() {
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || defined(OS_MACOSX)
   return true;
-#elif !defined(OS_WIN) && !defined(OS_MACOSX) && !defined(USE_AURA)
+#elif !defined(OS_WIN) && !defined(USE_AURA)
   return false;
 #endif