Use a resource throttle to implement shouldOverrideUrlLoading.

content/child/web_url_loader_impl.cc

 // Copyright 2014 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 "content/child/web_url_loader_impl.h"
 
 #include <algorithm>
 #include <deque>
 #include <string>
 
@@ skipping 724 matching lines @@
     ftp_listing_delegate_.reset(NULL);
   } else if (multipart_delegate_) {
     multipart_delegate_->OnCompletedRequest();
     multipart_delegate_.reset(NULL);
   }
 
   if (client_) {
     if (error_code != net::OK) {
       client_->didFail(
           loader_,
-          CreateWebURLError(request_.url(), stale_copy_in_cache, error_code));
+          CreateWebURLError(request_.url(), stale_copy_in_cache, error_code,
+              was_ignored_by_handler));
     } else {
       if (request_.useStreamOnResponse()) {
         got_all_stream_body_data_ = true;
         if (body_stream_buffer_.empty()) {
           // Close the handle to notify the end of data.
           body_stream_writer_.reset();
           client_->didFinishLoading(
               loader_, (completion_time - TimeTicks()).InSecondsF(),
               total_transfer_size);
         }
@@ skipping 361 matching lines @@
                                          int intra_priority_value) {
   context_->DidChangePriority(new_priority, intra_priority_value);
 }
 
 bool WebURLLoaderImpl::attachThreadedDataReceiver(
     blink::WebThreadedDataReceiver* threaded_data_receiver) {
   return context_->AttachThreadedDataReceiver(threaded_data_receiver);
 }
 
 }  // namespace content