Keep a separate list of :host(-context) rules.

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 156 matching lines @@
     }
 
     if (element.isLink())
         collectMatchingRulesForList(matchRequest.ruleSet->linkPseudoClassRules(), cascadeScope, cascadeOrder, matchRequest, ruleRange);
     if (SelectorChecker::matchesFocusPseudoClass(element))
         collectMatchingRulesForList(matchRequest.ruleSet->focusPseudoClassRules(), cascadeScope, cascadeOrder, matchRequest, ruleRange);
     collectMatchingRulesForList(matchRequest.ruleSet->tagRules(element.localName()), cascadeScope, cascadeOrder, matchRequest, ruleRange);
     collectMatchingRulesForList(matchRequest.ruleSet->universalRules(), cascadeScope, cascadeOrder, matchRequest, ruleRange);
 }
 
+void ElementRuleCollector::collectMatchingShadowHostRules(const MatchRequest& matchRequest, RuleRange& ruleRange, CascadeScope cascadeScope, CascadeOrder cascadeOrder, bool matchingTreeBoundaryRules)
+{
+    collectMatchingRulesForList(matchRequest.ruleSet->shadowHostRules(), cascadeScope, cascadeOrder, matchRequest, ruleRange);
+}
+
 CSSRuleList* ElementRuleCollector::nestedRuleList(CSSRule* rule)
 {
     switch (rule->type()) {
     case CSSRule::MEDIA_RULE:
         return toCSSMediaRule(rule)->cssRules();
     case CSSRule::KEYFRAMES_RULE:
         return toCSSKeyframesRule(rule)->cssRules();
     case CSSRule::SUPPORTS_RULE:
         return toCSSSupportsRule(rule)->cssRules();
     default:
@@ skipping 157 matching lines @@
     // information about "scope".
     int firstRuleIndex = -1, lastRuleIndex = -1;
     RuleRange ruleRange(firstRuleIndex, lastRuleIndex);
     // FIXME: Verify whether it's ok to ignore CascadeScope here.
     collectMatchingRules(MatchRequest(ruleSet), ruleRange);
 
     return m_matchedRules && !m_matchedRules->isEmpty();
 }
 
 } // namespace blink