Use the alternate notification UI for Mac

chrome/browser/notifications/notification_ui_manager_mac.mm

Index: chrome/browser/notifications/notification_ui_manager_mac.mm
diff --git a/chrome/browser/notifications/notification_ui_manager_mac.mm b/chrome/browser/notifications/notification_ui_manager_mac.mm
index 9010beb0f6a5a1f207b9314b9cb2a1c3979dc445..f5fdf4a104605deda95e693d3c4c28935a558ca8 100644
--- a/chrome/browser/notifications/notification_ui_manager_mac.mm
+++ b/chrome/browser/notifications/notification_ui_manager_mac.mm
@@ -119,10 +119,11 @@ void NotificationUIManagerMac::Add(const Notification& notification,
   // TODO(miguelg): Implement support for buttons
   toast.get().hasActionButton = NO;
 
-  // Some functionality is only available in 10.9+
+  // Some functionality is only available in 10.9+ or requires private APIs
   // Icon
-  if ([toast respondsToSelector:@selector(setContentImage:)]) {
-    [toast setValue:notification.icon().ToNSImage() forKey:@"contentImage"];
+  if ([toast respondsToSelector:@selector(_identityImage)]) {
+    [toast setValue:notification.icon().ToNSImage() forKey:@"_identityImage"];
+    [toast setValue:@NO forKey:@"_identityImageHasBorder"];
   }
 
   // Tag