Fix a null AppCacheBackendImpl ptr crash in CompleteCrossSiteTransfer and re…

content/browser/appcache/appcache_request_handler.h

 // 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.
 
 #ifndef CONTENT_BROWSER_APPCACHE_APPCACHE_REQUEST_HANDLER_H_
 #define CONTENT_BROWSER_APPCACHE_APPCACHE_REQUEST_HANDLER_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
 #include "content/browser/appcache/appcache_entry.h"
 #include "content/browser/appcache/appcache_host.h"
 #include "content/common/content_export.h"
 #include "content/public/common/resource_type.h"
 
 namespace net {
 class NetworkDelegate;
 class URLRequest;
 class URLRequestJob;
 }  // namespace net
 
 namespace content {
 class AppCacheRequestHandlerTest;
+class AppCacheService;
 class AppCacheURLRequestJob;
 
 // An instance is created for each net::URLRequest. The instance survives all
 // http transactions involved in the processing of its net::URLRequest, and is
 // given the opportunity to hijack the request along the way. Callers
 // should use AppCacheHost::CreateRequestHandler to manufacture instances
 // that can retrieve resources for a particular host.
 class CONTENT_EXPORT AppCacheRequestHandler
     : public base::SupportsUserData::Data,
       public AppCacheHost::Observer,
@@ skipping 12 matching lines @@
   AppCacheURLRequestJob* MaybeLoadFallbackForResponse(
       net::URLRequest* request,
       net::NetworkDelegate* network_delegate);
 
   void GetExtraResponseInfo(int64_t* cache_id, GURL* manifest_url);
 
   // Methods to support cross site navigations.
   void PrepareForCrossSiteTransfer(int old_process_id);
   void CompleteCrossSiteTransfer(int new_process_id, int new_host_id);
   void MaybeCompleteCrossSiteTransferInOldProcess(int old_process_id);
+  bool SanityCheckIsSameService(AppCacheService* service) {

[jsbell, 2016/01/14 22:52:29]

Add brief documentation here, i.e. why anyone would call this?

+    return !host_ || (host_->service() == service);
+  }
 
   static bool IsMainResourceType(ResourceType type) {
     return IsResourceTypeFrame(type) ||
            type == RESOURCE_TYPE_SHARED_WORKER;
   }
 
  private:
   friend class AppCacheHost;
 
   // Callers should use AppCacheHost::CreateRequestHandler.
@@ skipping 113 matching lines @@
   int cache_id_;
   GURL manifest_url_;
 
   friend class content::AppCacheRequestHandlerTest;
   DISALLOW_COPY_AND_ASSIGN(AppCacheRequestHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_APPCACHE_APPCACHE_REQUEST_HANDLER_H_