Introduce Node::containingTreeScope(), which asserts that the node's root is a tree scope

third_party/WebKit/Source/core/css/ElementRuleCollector.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 93 matching lines @@
     if (!propertySet)
         return;
     m_result.addMatchedProperties(propertySet);
     if (!isCacheable)
         m_result.setIsCacheable(false);
 }
 
 static bool rulesApplicableInCurrentTreeScope(const Element* element, const ContainerNode* scopingNode)
 {
     // Check if the rules come from a shadow style sheet in the same tree scope.
-    return !scopingNode || element->treeScope() == scopingNode->treeScope();
+    return !scopingNode || element->containingTreeScope() == scopingNode->containingTreeScope();
 }
 
 template<typename RuleDataListType>
 void ElementRuleCollector::collectMatchingRulesForList(const RuleDataListType* rules, CascadeOrder cascadeOrder, const MatchRequest& matchRequest)
 {
     if (!rules)
         return;
 
     SelectorChecker::Init init;
     init.mode = m_mode;
@@ skipping 204 matching lines @@
     // should not see the element's treescope. Because RuleSet has no
     // information about "scope".
     MatchRequest matchRequest(ruleSet);
     collectMatchingRules(matchRequest);
     collectMatchingShadowHostRules(matchRequest);
 
     return !m_matchedRules.isEmpty();
 }
 
 } // namespace blink