Don't request missing favicon on every page request.

content/common/image_messages.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.
 
 // Multiply-included message file, no traditional include guard.
 #include <vector>
 
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_param_traits.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
 #define IPC_MESSAGE_START ImageMsgStart
 
 // Messages sent from the browser to the renderer.
 
 // Requests the renderer to download the specified image, decode it,
 // and send the image data back via ImageHostMsg_DidDownloadImage.
 IPC_MESSAGE_ROUTED4(ImageMsg_DownloadImage,
                     int /* identifier for the request */,
                     GURL /* URL of the image */,
                     bool /* is favicon (turn off cookies) */,
                     int /* Preferred image size. Passed on to
                            ImageHostMsg_DidDownloadFavicon, unused otherwise */)
 
 // Messages sent from the renderer to the browser.
 
-IPC_MESSAGE_ROUTED4(ImageHostMsg_DidDownloadImage,
+IPC_MESSAGE_ROUTED5(ImageHostMsg_DidDownloadImage,
                     int /* Identifier of the request */,
+                    int /* HTTP response status */,
                     GURL /* URL of the image */,
                     int /* Preferred image size passed to
                            ImageMsg_DownloadImage */,
                     std::vector<SkBitmap> /* image_data */)