Oilpan: account for DocumentThreadableLoader::m_document back ref.

third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013, Intel Corporation
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 129 matching lines @@
 
         void loadRequest(const ResourceRequest&, ResourceLoaderOptions);
         bool isAllowedRedirect(const KURL&) const;
         bool isAllowedByContentSecurityPolicy(const KURL&, ContentSecurityPolicy::RedirectStatus) const;
         // Returns DoNotAllowStoredCredentials
         // if m_forceDoNotAllowStoredCredentials is set. Otherwise, just
         // returns allowCredentials value of m_resourceLoaderOptions.
         StoredCredentials effectiveAllowCredentials() const;
 
         SecurityOrigin* securityOrigin() const;
+        Document& document() const;
 
         ThreadableLoaderClient* m_client;
-        Document& m_document;
+        RawPtrWillBeWeakPersistent<Document> m_document;
 
         const ThreadableLoaderOptions m_options;
         // Some items may be overridden by m_forceDoNotAllowStoredCredentials
         // and m_securityOrigin. In such a case, build a ResourceLoaderOptions
         // with up-to-date values from them and this variable, and use it.
         const ResourceLoaderOptions m_resourceLoaderOptions;
 
         bool m_forceDoNotAllowStoredCredentials;
         RefPtr<SecurityOrigin> m_securityOrigin;
 
@@ skipping 32 matching lines @@
         // But this value is not the max number of total redirects allowed,
         // because same-origin redirects are not counted here.
         int m_corsRedirectLimit;
 
         const WebURLRequest::FetchRedirectMode m_redirectMode;
     };
 
 } // namespace blink
 
 #endif // DocumentThreadableLoader_h