Make the id used in IconMsg_DownloadFavicon unique

chrome/browser/favicon/favicon_tab_helper.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 CHROME_BROWSER_FAVICON_FAVICON_TAB_HELPER_H_
 #define CHROME_BROWSER_FAVICON_FAVICON_TAB_HELPER_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 56 matching lines @@
                     history::IconType icon_type,
                     const ImageDownloadCallback& callback);
 
   // Message Handler.  Must be public, because also called from
   // PrerenderContents.
   void OnUpdateFaviconURL(int32 page_id,
                           const std::vector<FaviconURL>& candidates);
 
   // FaviconHandlerDelegate methods.
   virtual content::NavigationEntry* GetActiveEntry() OVERRIDE;
-  virtual void StartDownload(int id, const GURL& url, int image_size) OVERRIDE;
+  virtual int StartDownload(const GURL& url, int image_size) OVERRIDE;
   virtual void NotifyFaviconUpdated() OVERRIDE;
 
  private:
   // content::WebContentsObserver overrides.
   virtual void NavigateToPendingEntry(
       const GURL& url,
       content::NavigationController::ReloadType reload_type) OVERRIDE;
   virtual void DidNavigateMainFrame(
       const content::LoadCommittedDetails& details,
       const content::FrameNavigateParams& params) OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
   void OnDidDownloadFavicon(int id,
                             const GURL& image_url,
                             bool errored,
                             const SkBitmap& image);
 
   Profile* profile_;
 
   scoped_ptr<FaviconHandler> favicon_handler_;
 
   // Handles downloading touchicons. It is NULL if
   // browser_defaults::kEnableTouchIcon is false.
   scoped_ptr<FaviconHandler> touch_icon_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(FaviconTabHelper);
 };
 
 #endif  // CHROME_BROWSER_FAVICON_FAVICON_TAB_HELPER_H_