Get rid of TreeBoundaryCrossingRules.

Source/core/dom/StyleEngine.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 44 matching lines @@
     : m_document(&document)
     , m_isMaster(!document.importsController() || document.importsController()->master() == &document)
     , m_pendingStylesheets(0)
     , m_documentStyleSheetCollection(DocumentStyleSheetCollection::create(document))
     , m_documentScopeDirty(true)
     , m_usesSiblingRules(false)
     , m_usesFirstLineRules(false)
     , m_usesWindowInactiveSelector(false)
     , m_usesRemUnits(false)
     , m_maxDirectAdjacentSelectors(0)
+    , m_treeBoundaryCrossingScopeCount(0)
     , m_ignorePendingStylesheets(false)
     , m_didCalculateResolver(false)
     // We don't need to create CSSFontSelector for imported document or
     // HTMLTemplateElement's document, because those documents have no frame.
     , m_fontSelector(document.frame() ? CSSFontSelector::create(&document) : nullptr)
 {
     if (m_fontSelector)
         m_fontSelector->registerForInvalidationCallbacks(this);
 }
 
@@ skipping 711 matching lines @@
     visitor->trace(m_dirtyTreeScopes);
     visitor->trace(m_activeTreeScopes);
     visitor->trace(m_fontSelector);
     visitor->trace(m_textToSheetCache);
     visitor->trace(m_sheetToTextCache);
 #endif
     CSSFontSelectorClient::trace(visitor);
 }
 
 }