Don't run PerformCheckpoint on Document::finishedParsing while running JS

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.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 4754 matching lines @@
     if (!m_documentTiming.domContentLoadedEventStart())
         m_documentTiming.markDomContentLoadedEventStart();
     dispatchEvent(Event::createBubble(EventTypeNames::DOMContentLoaded));
     if (!m_documentTiming.domContentLoadedEventEnd())
         m_documentTiming.markDomContentLoadedEventEnd();
     setParsingState(FinishedParsing);
 
     // 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());
+    if (!V8PerIsolateData::mainThreadIsolate()->InContext())
+        Microtask::performCheckpoint(V8PerIsolateData::mainThreadIsolate());
 
     if (LocalFrame* frame = this->frame()) {
         // 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 mainResourceWasAlreadyRequested = frame->loader().stateMachine()->committedFirstRealDocumentLoad();
 
         // FrameLoader::finishedParsing() might end up calling Document::implicitClose() if all
         // resource loads are complete. HTMLObjectElements can start loading their resources from
         // post attach callbacks triggered by recalcStyle().  This means if we parse out an <object>
@@ skipping 1188 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().getString().utf8().data());
 }
 #endif