Clarify when DocumentLoader's FrameLoader/FrameLoaderClient accessors can be used

third_party/WebKit/Source/web/WebDataSourceImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 #include "wtf/PtrUtil.h"
 #include <memory>
 
 namespace blink {
 
 WebDataSourceImpl* WebDataSourceImpl::create(
     LocalFrame* frame,
     const ResourceRequest& request,
     const SubstituteData& data,
     ClientRedirectPolicy clientRedirectPolicy) {
+  DCHECK(frame);
+
   return new WebDataSourceImpl(frame, request, data, clientRedirectPolicy);
 }
 
 const WebURLRequest& WebDataSourceImpl::originalRequest() const {
   return m_originalRequestWrapper;
 }
 
 const WebURLRequest& WebDataSourceImpl::getRequest() const {
   return m_requestWrapper;
 }
@@ skipping 100 matching lines @@
 void WebDataSourceImpl::setSubresourceFilter(
     WebDocumentSubresourceFilter* subresourceFilter) {
   DocumentLoader::setSubresourceFilter(WTF::wrapUnique(subresourceFilter));
 }
 
 DEFINE_TRACE(WebDataSourceImpl) {
   DocumentLoader::trace(visitor);
 }
 
 }  // namespace blink