Don't request missing favicon on every page request.

chrome/browser/favicon/favicon_tab_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_FAVICON_FAVICON_TAB_HELPER_H_
 #define CHROME_BROWSER_FAVICON_FAVICON_TAB_HELPER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 54 matching lines @@
       const std::vector<content::FaviconURL>& candidates) OVERRIDE;
 
   // Saves the favicon for the current page.
   void SaveFavicon();
 
   // FaviconHandlerDelegate methods.
   virtual content::NavigationEntry* GetActiveEntry() OVERRIDE;
   virtual int StartDownload(const GURL& url, int image_size) OVERRIDE;
   virtual void NotifyFaviconUpdated(bool icon_url_changed) OVERRIDE;
 
+  // Favicon download callback.
+  void DidDownloadFavicon(

[mef, 2013/05/08 20:20:01]

I've made it public so I could access it from unit test. I'm not very happy
about this and would love suggestions on avoiding this.

+      int id,
+      int http_status_code,
+      const GURL& image_url,
+      int requested_size,
+      const std::vector<SkBitmap>& bitmaps);
+
  private:
   explicit FaviconTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<FaviconTabHelper>;
 
   // 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;
 
-  // Favicon download callback.
-  void DidDownloadFavicon(
-      int id,
-      const GURL& image_url,
-      int requested_size,
-      const std::vector<SkBitmap>& bitmaps);
-
   Profile* profile_;
   bool should_fetch_icons_;
 
   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_