Oilpan: Move MainThreadTaskRunner into Oilpan heap.

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 5642 matching lines @@
     visitor->trace(m_visitedLinkState);
     visitor->trace(m_frame);
     visitor->trace(m_domWindow);
     visitor->trace(m_fetcher);
     visitor->trace(m_parser);
     visitor->trace(m_contextFeatures);
     visitor->trace(m_styleSheetList);
     visitor->trace(m_documentTiming);
     visitor->trace(m_mediaQueryMatcher);
     visitor->trace(m_scriptedAnimationController);
+    visitor->trace(m_taskRunner);
     visitor->trace(m_textAutosizer);
     visitor->trace(m_registrationContext);
     visitor->trace(m_customElementMicrotaskRunQueue);
     visitor->trace(m_elementDataCache);
     visitor->trace(m_associatedFormControls);
     visitor->trace(m_useElementsNeedingUpdate);
     visitor->trace(m_layerUpdateSVGFilterElements);
     visitor->trace(m_timers);
     visitor->trace(m_templateDocument);
     visitor->trace(m_templateDocumentHost);
@@ skipping 20 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().string().utf8().data());
 }
 #endif