Don't request missing favicon on every page request.

chrome/browser/ui/web_applications/web_app_ui.cc

 // 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.
 
 #include "chrome/browser/ui/web_applications/web_app_ui.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
@@ skipping 71 matching lines @@
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details);
 
   // Downloads icon via the FaviconTabHelper.
   void DownloadIcon();
 
   // Favicon download callback.
   void DidDownloadFavicon(
       int id,
+      int http_status_code,
       const GURL& image_url,
       int requested_size,
       const std::vector<SkBitmap>& bitmaps);
 
   // Checks if shortcuts exists on desktop, start menu and quick launch.
   void CheckExistingShortcuts();
 
   // Update shortcut files and icons.
   void UpdateShortcuts();
   void UpdateShortcutsOnFileThread();
@@ skipping 83 matching lines @@
       true,  // favicon
       std::max(unprocessed_icons_.back().width,
                unprocessed_icons_.back().height),
       base::Bind(&UpdateShortcutWorker::DidDownloadFavicon,
                  base::Unretained(this)));
   unprocessed_icons_.pop_back();
 }
 
 void UpdateShortcutWorker::DidDownloadFavicon(
     int id,
+    int http_status_code,
     const GURL& image_url,
     int requested_size,
     const std::vector<SkBitmap>& bitmaps) {
   std::vector<ui::ScaleFactor> scale_factors;
   scale_factors.push_back(ui::SCALE_FACTOR_100P);
 
   size_t closest_index =
       FaviconUtil::SelectBestFaviconFromBitmaps(bitmaps,
                                                 scale_factors,
                                                 requested_size);
@@ skipping 268 matching lines @@
   }
 
   // |info_list| may still be empty at this point, in which case LoadImage
   // will call the OnImageLoaded callback with an empty image and exit
   // immediately.
   extensions::ImageLoader::Get(profile)->LoadImagesAsync(&extension, info_list,
       base::Bind(&OnImageLoaded, shortcut_info, callback));
 }
 
 }  // namespace web_app