Implemented ExternalData interface on DownloadItem and used it for SafeBrowsing.

content/browser/download/download_item.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.
 //
 // Each download is represented by a DownloadItem, and all DownloadItems
 // are owned by the DownloadManager which maintains a global list of all
 // downloads. DownloadItems are created when a user initiates a download,
 // and exist for the duration of the browser life time.
 //
 // Download observers:
 //   DownloadItem::Observer:
 //     - allows observers to receive notifications about one download from start
 //       to completion
 // Use AddObserver() / RemoveObserver() on the appropriate download object to
 // receive state updates.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_H_
 #pragma once
 
+#include <map>
 #include <string>
 
 #include "base/string16.h"
 #include "content/browser/download/download_state_info.h"
 #include "content/browser/download/interrupt_reasons.h"
 
 class DownloadId;
 class DownloadFileManager;
 class DownloadManager;
 class FilePath;
@@ skipping 62 matching lines @@
    public:
     virtual void OnDownloadUpdated(DownloadItem* download) = 0;
 
     // Called when a downloaded file has been opened.
     virtual void OnDownloadOpened(DownloadItem* download) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
+  // Interface for data that can be stored associated with (and owned
+  // by) an object of this class via GetExternalData/SetExternalData.
+  class ExternalData {
+   public:
+    virtual ~ExternalData() {};
+  };
+
   virtual ~DownloadItem();
 
   virtual void AddObserver(DownloadItem::Observer* observer) = 0;
   virtual void RemoveObserver(DownloadItem::Observer* observer) = 0;
 
   // Notifies our observers periodically.
   virtual void UpdateObservers() = 0;
 
   // Returns true if it is OK to open a folder which this file is inside.
   virtual bool CanShowInFolder() = 0;
@@ skipping 188 matching lines @@
   virtual bool NeedsRename() const = 0;
 
   // Cancels the off-thread aspects of the download.
   // TODO(rdsmith): This should be private and only called from
   // DownloadItem::Cancel/Interrupt; it isn't now because we can't
   // call those functions from
   // DownloadManager::FileSelectionCancelled() without doing some
   // rewrites of the DownloadManager queues.
   virtual void OffThreadCancel(DownloadFileManager* file_manager) = 0;
 
+  // Manage data owned by other subsystems associated with the
+  // DownloadItem.  By custom, key is the address of a
+  // static char subsystem_specific_string[] = ".."; defined
+  // in the subsystem, but the only requirement of this interface
+  // is that the key be unique over all data stored with this
+  // DownloadItem.
+  //
+  // Note that SetExternalData takes ownership of the
+  // passed object; it will be destroyed when the DownloadItem is.
+  // If an object is already held by the DownloadItem associated with
+  // the passed key, it will be destroyed on overwrite.

[asanka, 2011/12/07 04:10:57]

Nit: Should this mention the behavior when the object already held is the same
as the new one being set?

[Randy Smith (Not in Mondays), 2011/12/07 18:36:12]

Done.

+  virtual ExternalData* GetExternalData(const void* key) = 0;
+  virtual void SetExternalData(const void* key, ExternalData* data) = 0;
+
   virtual std::string DebugString(bool verbose) const = 0;
 
   virtual void MockDownloadOpenForTesting() = 0;
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_H_