BrowserContext should simply own DownloadManager

content/browser/download/download_manager_impl.h

Index: content/browser/download/download_manager_impl.h
diff --git a/content/browser/download/download_manager_impl.h b/content/browser/download/download_manager_impl.h
index bbdd0856ac6af37fa1459019aeb5e049c9659e90..2a9cdd0ca08899f5a4cca501dd26b89d6b3b417b 100644
--- a/content/browser/download/download_manager_impl.h
+++ b/content/browser/download/download_manager_impl.h
@@ -93,6 +93,8 @@ class CONTENT_EXPORT DownloadManagerImpl : public DownloadManager,
       scoped_ptr<DownloadFileFactory> file_factory);
   virtual DownloadFileFactory* GetDownloadFileFactoryForTesting();
 
+  virtual ~DownloadManagerImpl();
+
  private:
   typedef std::set<DownloadItem*> DownloadSet;
   typedef base::hash_map<int32, DownloadItemImpl*> DownloadMap;
@@ -102,10 +104,6 @@ class CONTENT_EXPORT DownloadManagerImpl : public DownloadManager,
   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,
@@ -166,6 +164,8 @@ class CONTENT_EXPORT DownloadManagerImpl : public DownloadManager,
 
   net::NetLog* net_log_;
 
+  base::WeakPtrFactory<DownloadManagerImpl> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadManagerImpl);
 };