Update first download notification correctly if there are multiple notifications

chrome/browser/download/notification/download_notification_manager.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_MANAGER_H_
 #define CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_MANAGER_H_
 
 #include <set>
 
 #include "chrome/browser/download/download_ui_controller.h"
@@ skipping 27 matching lines @@
       items_deleter_;
 };
 
 class DownloadNotificationManagerForProfile
     : public content::DownloadItem::Observer {
  public:
   DownloadNotificationManagerForProfile(
       Profile* profile, DownloadNotificationManager* parent_manager);
   ~DownloadNotificationManagerForProfile() override;
 
+  message_center::MessageCenter* message_center() const {
+    return message_center_;
+  }
+
   // DownloadItem::Observer overrides:
   void OnDownloadUpdated(content::DownloadItem* download) override;
   void OnDownloadOpened(content::DownloadItem* download) override;
   void OnDownloadRemoved(content::DownloadItem* download) override;
   void OnDownloadDestroyed(content::DownloadItem* download) override;
 
   void OnNewDownloadReady(content::DownloadItem* item);
 
  private:
   friend class test::DownloadItemNotificationTest;
 
+  void OverrideMessageCenterForTest(
+      message_center::MessageCenter* message_center);
+
   Profile* profile_ = nullptr;
   DownloadNotificationManager* parent_manager_;  // weak
   std::set<content::DownloadItem*> downloading_items_;
   std::map<content::DownloadItem*, DownloadItemNotification*> items_;
 
+  // Pointer to the message center instance.
+  message_center::MessageCenter* message_center_;
+
   STLValueDeleter<std::map<content::DownloadItem*, DownloadItemNotification*>>
       items_deleter_;
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_MANAGER_H_