Remove kDisableDownloadNotification and stop compiling shelf code on

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"
 #include "chrome/browser/download/notification/download_item_notification.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/download_item.h"
 
 class DownloadNotificationManagerForProfile;
 
 class DownloadNotificationManager : public DownloadUIController::Delegate {
  public:
-  static bool IsEnabled();
-
   explicit DownloadNotificationManager(Profile* profile);
   ~DownloadNotificationManager() override;
 
   void OnAllDownloadsRemoving(Profile* profile);
   // DownloadUIController::Delegate:
   void OnNewDownloadReady(content::DownloadItem* item) override;
 
   DownloadNotificationManagerForProfile* GetForProfile(Profile* profile) const;
 
  private:
@@ skipping 38 matching lines @@
   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_