mac: Minor tweaks to notifications code.

ui/message_center/cocoa/popup_collection.mm

Index: ui/message_center/cocoa/popup_collection.mm
diff --git a/ui/message_center/cocoa/popup_collection.mm b/ui/message_center/cocoa/popup_collection.mm
index 60547e0b95c0b448b14df1caeb1322dfe5135ff2..bf3df413235d10096f2b29e806c94bb543919ed1 100644
--- a/ui/message_center/cocoa/popup_collection.mm
+++ b/ui/message_center/cocoa/popup_collection.mm
@@ -51,10 +51,9 @@ class PopupCollectionObserver : public message_center::MessageCenterObserver {
 
   virtual void OnNotificationAdded(
       const std::string& notification_id) OVERRIDE {
-    const auto& popups = message_center_->GetPopupNotifications();
-    for (auto it = popups.begin(); it != popups.end(); ++it) {
-      if ((*it)->id() == notification_id) {
-        [popup_collection_ addNotification:*it];
+    for (const auto& notification : message_center_->GetPopupNotifications()) {
+      if (notification->id() == notification_id) {
+        [popup_collection_ addNotification:notification];
         return;
       }
     }