Remove unused fields from //content.

content/browser/download/download_manager_impl.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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 185 matching lines @@
   // TODO(asanka): Remove this container in favor of downloads_by_guid_ as a
   // part of http://crbug.com/593020.
   DownloadMap downloads_;
 
   // Same as the above, but maps from GUID to download item. Note that the
   // container is case sensitive. Hence the key needs to be normalized to
   // upper-case when inserting new elements here. Fortunately for us,
   // DownloadItemImpl already normalizes the string GUID.
   DownloadGuidMap downloads_by_guid_;
 
-  int history_size_;
-
   // True if the download manager has been initialized and requires a shutdown.
   bool shutdown_needed_;
 
   // Observers that want to be notified of changes to the set of downloads.
   base::ObserverList<Observer> observers_;
 
   // The current active browser context.
   BrowserContext* browser_context_;
 
   // Allows an embedder to control behavior. Guaranteed to outlive this object.
   DownloadManagerDelegate* delegate_;
 
   net::NetLog* net_log_;
 
   std::vector<std::unique_ptr<UrlDownloader, BrowserThread::DeleteOnIOThread>>
       url_downloaders_;
 
   base::WeakPtrFactory<DownloadManagerImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadManagerImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_IMPL_H_