Renamed :host to :ancestor and made :host to match only shadow host.

Source/core/css/SelectorChecker.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 830 matching lines @@
                     return true;
                 break;
             }
 
         case CSSSelector::PseudoUnresolved:
             if (element.isUnresolvedCustomElement())
                 return true;
             break;
 
         case CSSSelector::PseudoHost:
+        case CSSSelector::PseudoAncestor:
             {
                 // :host only matches a shadow host when :host is in a shadow tree of the shadow host.
                 if (!context.scope || !(context.behaviorAtBoundary & ScopeIsShadowHost) || context.scope != element)
                     return false;
                 ASSERT(element.shadow());
 
                 // For empty parameter case, i.e. just :host or :host().
                 if (!selector->selectorList()) // Use *'s specificity. So just 0.
                     return true;
 
                 SelectorCheckingContext subContext(context);
                 subContext.isSubSelector = true;
 
                 bool matched = false;
                 unsigned maxSpecificity = 0;
 
                 // If one of simple selectors matches an element, returns SelectorMatches. Just "OR".
                 for (subContext.selector = selector->selectorList()->first(); subContext.selector; subContext.selector = CSSSelectorList::next(subContext.selector)) {
                     subContext.behaviorAtBoundary = ScopeIsShadowHostInPseudoHostParameter;
                     subContext.scope = context.scope;
                     // Use NodeRenderingTraversal to traverse a composed ancestor list of a given element.
-                    for (Element* nextElement = &element; nextElement; nextElement = NodeRenderingTraversal::parentElement(nextElement)) {
+                    Element* nextElement = &element;
+                    do {
                         MatchResult subResult;
                         subContext.element = nextElement;
                         if (match(subContext, siblingTraversalStrategy, &subResult) == SelectorMatches) {
                             matched = true;
                             // Consider div:host(div:host(div:host(div:host...))).
                             maxSpecificity = std::max(maxSpecificity, subContext.selector->specificity() + subResult.specificity);
                             break;
                         }
                         subContext.behaviorAtBoundary = DoesNotCrossBoundary;
                         subContext.scope = 0;
-                    }
+
+                        if (selector->pseudoType() == CSSSelector::PseudoHost)
+                            break;
+
+                        nextElement = NodeRenderingTraversal::parentElement(nextElement);
+                    } while (nextElement);
                 }
                 if (matched) {
                     if (specificity)
                         *specificity = maxSpecificity;
                     return true;
                 }
             }
             break;
 
         case CSSSelector::PseudoHorizontal:
@@ skipping 167 matching lines @@
     return element.focused() && isFrameFocused(element);
 }
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const DOMSiblingTraversalStrategy&, MatchResult*) const;
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const ShadowDOMSiblingTraversalStrategy&, MatchResult*) const;
 
 }