Fix a null AppCacheBackendImpl ptr crash in CompleteCrossSiteTransfer and re…

content/browser/appcache/appcache_request_handler.cc

 // Copyright (c) 2011 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/browser/appcache/appcache_request_handler.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "content/browser/appcache/appcache.h"
@@ skipping 169 matching lines @@
 void AppCacheRequestHandler::GetExtraResponseInfo(int64_t* cache_id,
                                                   GURL* manifest_url) {
   *cache_id = cache_id_;
   *manifest_url = manifest_url_;
 }
 
 void AppCacheRequestHandler::PrepareForCrossSiteTransfer(int old_process_id) {
   if (!host_)
     return;
   AppCacheBackendImpl* backend = host_->service()->GetBackend(old_process_id);
+  DCHECK(backend) << "appcache detected likely storage partition mismatch";
   old_process_id_ = old_process_id;
   old_host_id_ = host_->host_id();
   host_for_cross_site_transfer_ = backend->TransferHostOut(host_->host_id());
   DCHECK_EQ(host_, host_for_cross_site_transfer_.get());
 }
 
 void AppCacheRequestHandler::CompleteCrossSiteTransfer(
     int new_process_id, int new_host_id) {
   if (!host_for_cross_site_transfer_.get())
     return;
   DCHECK_EQ(host_, host_for_cross_site_transfer_.get());
   AppCacheBackendImpl* backend = host_->service()->GetBackend(new_process_id);
+  DCHECK(backend) << "appcache detected likely storage partition mismatch";
   backend->TransferHostIn(new_host_id,
                           std::move(host_for_cross_site_transfer_));
 }
 
 void AppCacheRequestHandler::MaybeCompleteCrossSiteTransferInOldProcess(
     int old_process_id) {
   if (!host_ || !host_for_cross_site_transfer_.get() ||
       old_process_id != old_process_id_) {
     return;
   }
@@ skipping 268 matching lines @@
   if (!host_->associated_cache() ||
       !host_->associated_cache()->is_complete()) {
     DeliverNetworkResponse();
     return;
   }
 
   ContinueMaybeLoadSubResource();
 }
 
 }  // namespace content