Remove usage of SequencedWorkerPool::GetNamedSequenceToken from ChromeDownloadManagerDelegate.

chrome/browser/download/chrome_download_manager_delegate.h

 // Copyright (c) 2012 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_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 #define CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
 #include "chrome/browser/download/download_path_reservation_tracker.h"
 #include "chrome/browser/download/download_target_determiner_delegate.h"
 #include "chrome/browser/download/download_target_info.h"
 #include "chrome/browser/safe_browsing/download_protection_service.h"
 #include "content/public/browser/download_danger_type.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager_delegate.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/features/features.h"
@@ skipping 49 matching lines @@
       content::WebContents* web_contents,
       const base::FilePath& suggested_path,
       const base::FilePath::StringType& default_extension,
       bool can_save_as_complete,
       const content::SavePackagePathPickedCallback& callback) override;
   void SanitizeSavePackageResourceName(base::FilePath* filename) override;
   void OpenDownload(content::DownloadItem* download) override;
   void ShowDownloadInShell(content::DownloadItem* download) override;
   void CheckForFileExistence(
       content::DownloadItem* download,
-      const content::CheckForFileExistenceCallback& callback) override;
+      content::CheckForFileExistenceCallback callback) override;
   std::string ApplicationClientIdForFileScanning() const override;
 
   // Opens a download using the platform handler. DownloadItem::OpenDownload,
   // which ends up being handled by OpenDownload(), will open a download in the
   // browser if doing so is preferred.
   void OpenDownloadUsingPlatformHandler(content::DownloadItem* download);
 
   DownloadPrefs* download_prefs() { return download_prefs_.get(); }
 
  protected:
@@ skipping 62 matching lines @@
       std::unique_ptr<DownloadTargetInfo> target_info);
 
   // Returns true if |path| should open in the browser.
   bool IsOpenInBrowserPreferreredForFile(const base::FilePath& path);
 
   Profile* profile_;
   uint32_t next_download_id_;
   IdCallbackVector id_callbacks_;
   std::unique_ptr<DownloadPrefs> download_prefs_;
 
+  // SequencedTaskRunner to check for file existence. A sequence is used so that
+  // a large download history doesn't cause a large number of concurrent disk
+  // operations.
+  const scoped_refptr<base::SequencedTaskRunner>
+      check_for_file_existence_task_runner_;
+
 #if BUILDFLAG(ENABLE_EXTENSIONS)
   // Maps from pending extension installations to DownloadItem IDs.
   typedef base::hash_map<extensions::CrxInstaller*,
       content::DownloadOpenDelayedCallback> CrxInstallerMap;
   CrxInstallerMap crx_installers_;
 #endif
 
   content::NotificationRegistrar registrar_;
 
   base::WeakPtrFactory<ChromeDownloadManagerDelegate> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeDownloadManagerDelegate);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_