Don't request missing favicon on every page request.

content/public/browser/web_contents.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 CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/process_util.h"
@@ skipping 390 matching lines @@
 
   // Returns true if the location bar should be focused by default rather than
   // the page contents. The view calls this function when the tab is focused
   // to see what it should do.
   virtual bool FocusLocationBarByDefault() = 0;
 
   // Does this have an opener associated with it?
   virtual bool HasOpener() const = 0;
 
   typedef base::Callback<void(int, /* id */
+                              int, /* HTTP status code */
                               const GURL&, /* image_url */
                               int,  /* requested_size */
                               const std::vector<SkBitmap>& /* bitmaps*/)>
       ImageDownloadCallback;
 
   // Sends a request to download the given image |url| and returns the unique
   // id of the download request. When the download is finished, |callback| will
   // be called with the bitmaps received from the renderer. If |is_favicon| is
   // true, the cookies are not sent and not accepted during download. Note that
   // |image_size| is a hint for images with multiple sizes. The downloaded image
   // is not resized to the given image_size. If 0 is passed, the first frame of
   // the image is returned.
   virtual int DownloadImage(const GURL& url,
                             bool is_favicon,
                             int image_size,
                             const ImageDownloadCallback& callback) = 0;
 
  private:
   // This interface should only be implemented inside content.
   friend class WebContentsImpl;
   WebContents() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_