The WebURLResponse will be null if the network request fails. So, a null che...

webkit/glue/alt_404_page_resource_fetcher.cc

 // Copyright (c) 2006-2008 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 "config.h"
 
 #include "base/compiler_specific.h"
 
 MSVC_PUSH_WARNING_LEVEL(0);
 #include "DocumentLoader.h"
@@ skipping 24 matching lines @@
       doc_loader_(doc_loader) {
 
   fetcher_.reset(new ResourceFetcherWithTimeout(
       url, WebFrameImpl::FromFrame(frame), kDownloadTimeoutSec,
       NewCallback(this, &Alt404PageResourceFetcher::OnURLFetchComplete)));
 }
 
 void Alt404PageResourceFetcher::OnURLFetchComplete(
     const WebURLResponse& response,
     const std::string& data) {
-  if (response.httpStatusCode() == 200) {
+  if (!response.isNull() && response.httpStatusCode() == 200) {
     // Only show server response if we got a 200.
     webframeloaderclient_->Alt404PageFinished(doc_loader_.get(), data);
   } else {
     webframeloaderclient_->Alt404PageFinished(doc_loader_.get(), std::string());
   }
   doc_loader_ = NULL;
 }
 
 }  // namespace webkit_glue