BrowserContext should simply own DownloadManager

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 <map>
 #include <set>
 
@@ skipping 75 matching lines @@
   virtual void CheckForHistoryFilesRemoval() OVERRIDE;
   virtual DownloadItem* GetDownload(int id) OVERRIDE;
 
   // For testing; specifically, accessed from TestFileErrorInjector.
   void SetDownloadItemFactoryForTesting(
       scoped_ptr<DownloadItemFactory> item_factory);
   void SetDownloadFileFactoryForTesting(
       scoped_ptr<DownloadFileFactory> file_factory);
   virtual DownloadFileFactory* GetDownloadFileFactoryForTesting();
 
+  virtual ~DownloadManagerImpl();

[sky, 2013/05/23 21:55:53]

Destructor should be with constructor above (see style guide for full details).

Also, you should move your implementation to match new position.

+
  private:
   typedef std::set<DownloadItem*> DownloadSet;
   typedef base::hash_map<int32, DownloadItemImpl*> DownloadMap;
   typedef std::vector<DownloadItemImpl*> DownloadItemImplVector;
 
   // For testing.
   friend class DownloadManagerTest;
   friend class DownloadTest;
 
-  friend class base::RefCountedThreadSafe<DownloadManagerImpl>;
-
-  virtual ~DownloadManagerImpl();
-
   // Create a new active item based on the info.  Separate from
   // StartDownload() for testing.
   DownloadItemImpl* CreateActiveItem(DownloadId id,
                                      const DownloadCreateInfo& info);
 
   // Get next download id.
   DownloadId GetNextId();
 
   // Called with the result of DownloadManagerDelegate::CheckForFileExistence.
   // Updates the state of the file and then notifies this update to the file's
@@ skipping 40 matching lines @@
   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_;
 
+  base::WeakPtrFactory<DownloadManagerImpl> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadManagerImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_IMPL_H_