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

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 3014 matching lines @@
     SetReadyState(kComplete);
   CheckCompleted();
 }
 
 void Document::ImplicitClose() {
   DCHECK(!InStyleRecalc());
   DCHECK(parser_);
 
   load_event_progress_ = kLoadEventInProgress;
 
-  ScriptableDocumentParser* parser = GetScriptableDocumentParser();
-  well_formed_ = parser && parser->WellFormed();
-
   // We have to clear the parser, in case someone document.write()s from the
   // onLoad event handler, as in Radar 3206524.
   DetachParser();
 
   if (GetFrame() && CanExecuteScripts(kNotAboutToExecuteScript)) {
     ImageLoader::DispatchPendingLoadEvents();
     ImageLoader::DispatchPendingErrorEvents();
   }
 
   // JS running below could remove the frame or destroy the LayoutView so we
@@ skipping 2446 matching lines @@
   DispatchEvent(Event::CreateBubble(EventTypeNames::DOMContentLoaded));
   if (!document_timing_.DomContentLoadedEventEnd())
     document_timing_.MarkDomContentLoadedEventEnd();
   SetParsingState(kFinishedParsing);
 
   // Ensure Custom Element callbacks are drained before DOMContentLoaded.
   // FIXME: Remove this ad-hoc checkpoint when DOMContentLoaded is dispatched in
   // a queued task, which will do a checkpoint anyway. https://crbug.com/425790
   Microtask::PerformCheckpoint(V8PerIsolateData::MainThreadIsolate());
 
+  ScriptableDocumentParser* parser = GetScriptableDocumentParser();
+  well_formed_ = parser && parser->WellFormed();
+
   if (LocalFrame* frame = this->GetFrame()) {
     // Don't update the layout tree if we haven't requested the main resource
     // yet to avoid adding extra latency. Note that the first layout tree update
     // can be expensive since it triggers the parsing of the default stylesheets
     // which are compiled-in.
     const bool main_resource_was_already_requested =
         frame->Loader().StateMachine()->CommittedFirstRealDocumentLoad();
 
     // FrameLoader::finishedParsing() might end up calling
     // Document::implicitClose() if all resource loads are
@@ skipping 1300 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->Url().GetString().Utf8().data());
 }
 #endif