Use a resource throttle to implement shouldOverrideUrlLoading.

content/common/frame_messages.h

 // Copyright 2013 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.
 
 // IPC messages for interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include "content/common/content_export.h"
 #include "content/common/content_param_traits.h"
 #include "content/common/frame_message_enums.h"
@@ skipping 100 matching lines @@
   // Error code as reported in the DidFailProvisionalLoad callback.
   IPC_STRUCT_MEMBER(int, error_code)
   // An error message generated from the error_code. This can be an empty
   // string if we were unable to find a meaningful description.
   IPC_STRUCT_MEMBER(base::string16, error_description)
   // The URL that the error is reported for.
   IPC_STRUCT_MEMBER(GURL, url)
   // True if the failure is the result of navigating to a POST again
   // and we're going to show the POST interstitial.
   IPC_STRUCT_MEMBER(bool, showing_repost_interstitial)
+  IPC_STRUCT_MEMBER(bool, was_ignored_by_handler)
 IPC_STRUCT_END()
 
 IPC_STRUCT_TRAITS_BEGIN(content::FrameNavigateParams)
   IPC_STRUCT_TRAITS_MEMBER(page_id)
   IPC_STRUCT_TRAITS_MEMBER(nav_entry_id)
   IPC_STRUCT_TRAITS_MEMBER(url)
   IPC_STRUCT_TRAITS_MEMBER(base_url)
   IPC_STRUCT_TRAITS_MEMBER(referrer)
   IPC_STRUCT_TRAITS_MEMBER(transition)
   IPC_STRUCT_TRAITS_MEMBER(redirects)
@@ skipping 537 matching lines @@
 
 // Notifies the browser that a frame in the view has changed. This message
 // has a lot of parameters and is packed/unpacked by functions defined in
 // render_messages.h.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidCommitProvisionalLoad,
                     FrameHostMsg_DidCommitProvisionalLoad_Params)
 
 // Notifies the browser that a document has been loaded.
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidFinishDocumentLoad)
 
-IPC_MESSAGE_ROUTED3(FrameHostMsg_DidFailLoadWithError,
+IPC_MESSAGE_ROUTED4(FrameHostMsg_DidFailLoadWithError,
                     GURL /* validated_url */,
                     int /* error_code */,
-                    base::string16 /* error_description */)
+                    base::string16 /* error_description */,
+                    bool /* was_ignored_by_handler */)
 
 // Sent when the renderer decides to ignore a navigation.
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidDropNavigation)
 
 // Sent when the renderer starts loading the page. |to_different_document| will
 // be true unless the load is a fragment navigation, or triggered by
 // history.pushState/replaceState.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidStartLoading,
                     bool /* to_different_document */)
 
@@ skipping 267 matching lines @@
                     FrameMsg_PostMessage_Params)
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
 
 // Message to show/hide a popup menu using native controls.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_ShowPopup,
                     FrameHostMsg_ShowPopup_Params)
 IPC_MESSAGE_ROUTED0(FrameHostMsg_HidePopup)
 
 #endif