Implemented ExternalData interface on DownloadItem and used it for SafeBrowsing.

content/browser/download/download_item_impl.h

 // Copyright (c) 2011 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_ITEM_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_
 #pragma once
 
 #include <string>
 
@@ skipping 184 matching lines @@
   virtual DownloadStateInfo GetStateInfo() const OVERRIDE;
   virtual content::BrowserContext* BrowserContext() const OVERRIDE;
   virtual TabContents* GetTabContents() const OVERRIDE;
   virtual FilePath GetTargetFilePath() const OVERRIDE;
   virtual FilePath GetFileNameToReportUser() const OVERRIDE;
   virtual FilePath GetUserVerifiedFilePath() const OVERRIDE;
   virtual bool NeedsRename() const OVERRIDE;
   virtual void OffThreadCancel(DownloadFileManager* file_manager) OVERRIDE;
   virtual std::string DebugString(bool verbose) const OVERRIDE;
   virtual void MockDownloadOpenForTesting() OVERRIDE;
+  virtual ExternalData* GetExternalData(const void* key) OVERRIDE;
+  virtual void SetExternalData(const void* key, ExternalData* data) OVERRIDE;
 
  private:
   // Construction common to all constructors. |active| should be true for new
   // downloads and false for downloads from the history.
   void Init(bool active);
 
   // Internal helper for maintaining consistent received and total sizes.
   void UpdateSize(int64 size);
 
   // Called when the entire download operation (including renaming etc)
@@ skipping 130 matching lines @@
   // be treated as though the user opened it.
   bool opened_;
 
   // Do we actual open downloads when requested?  For testing purposes
   // only.
   bool open_enabled_;
 
   // Did the delegate delay calling Complete on this download?
   bool delegate_delayed_complete_;
 
+  // External Data storage.  All objects in the store
+  // are owned by the DownloadItemImpl.
+  std::map<const void*, ExternalData*> external_data_map_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadItemImpl);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_IMPL_H_