Update first download notification correctly if there are multiple notifications

chrome/browser/download/notification/download_notification_manager.cc

Index: chrome/browser/download/notification/download_notification_manager.cc
diff --git a/chrome/browser/download/notification/download_notification_manager.cc b/chrome/browser/download/notification/download_notification_manager.cc
index a91349b7eb1ba9353247a27cd08291b6ce530216..6eb6b493bd565ab8ea65489517e83afc435913f4 100644
--- a/chrome/browser/download/notification/download_notification_manager.cc
+++ b/chrome/browser/download/notification/download_notification_manager.cc
@@ -78,6 +78,7 @@ DownloadNotificationManagerForProfile::DownloadNotificationManagerForProfile(
     DownloadNotificationManager* parent_manager)
     : profile_(profile),
       parent_manager_(parent_manager),
+      message_center_(g_browser_process->message_center()),
       items_deleter_(&items_) {
 }
 
@@ -153,3 +154,9 @@ void DownloadNotificationManagerForProfile::OnNewDownloadReady(
   DownloadItemNotification* item = new DownloadItemNotification(download, this);
   items_.insert(std::make_pair(download, item));
 }
+
+void DownloadNotificationManagerForProfile::OverrideMessageCenterForTest(
+    message_center::MessageCenter* message_center) {
+  DCHECK(message_center);
+  message_center_ = message_center;
+}