Style tag in an XHR's responseXML shouldn't make the responseXML be null.

third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp

 /*
  *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
  *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
  *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 1620 matching lines @@
   // This should only be called when response document is parsed asynchronously.
   DCHECK(response_document_parser_);
   DCHECK(!response_document_parser_->IsParsing());
 
   // Do nothing if we are called from |internalAbort()|.
   if (error_)
     return;
 
   ClearVariablesForLoading();
 
-  response_document_->CheckCompleted();
-
   if (!response_document_->WellFormed())
     response_document_ = nullptr;
 
   parsed_response_ = true;
 
   EndLoading();
 }
 
 void XMLHttpRequest::EndLoading() {
   probe::didFinishXHRLoading(GetExecutionContext(), this, this, method_, url_);
@@ skipping 238 matching lines @@
   visitor->TraceWrappers(response_document_);
   visitor->TraceWrappers(response_array_buffer_);
   XMLHttpRequestEventTarget::TraceWrappers(visitor);
 }
 
 std::ostream& operator<<(std::ostream& ostream, const XMLHttpRequest* xhr) {
   return ostream << "XMLHttpRequest " << static_cast<const void*>(xhr);
 }
 
 }  // namespace blink