Track connected subframes per-Document instead of per-Node.

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 5958 matching lines @@
     visitor->trace(m_cssTarget);
     visitor->trace(m_currentScriptStack);
     visitor->trace(m_scriptRunner);
     visitor->trace(m_listsInvalidatedAtDocument);
     for (int i = 0; i < numNodeListInvalidationTypes; ++i)
         visitor->trace(m_nodeLists[i]);
     visitor->trace(m_topLayerElements);
     visitor->trace(m_elemSheet);
     visitor->trace(m_nodeIterators);
     visitor->trace(m_ranges);
+    visitor->trace(m_subframeTracker);
     visitor->trace(m_styleEngine);
     visitor->trace(m_formController);
     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);
@@ skipping 36 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