Simplify UserAgentShadowRoot check for /deep/ selectors.

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 277 matching lines @@
     nextContext.hasSelectionPseudo = dynamicPseudo == SELECTION;
     if ((context.inRightmostCompound || m_mode == CollectingCSSRules || m_mode == CollectingStyleRules || m_mode == QueryingRules) && dynamicPseudo != NOPSEUDO
         && !nextContext.hasSelectionPseudo
         && !(nextContext.hasScrollbarPseudo && nextContext.selector->match() == CSSSelector::PseudoClass))
         return SelectorFailsCompletely;
 
     nextContext.isSubSelector = true;
     return matchSelector(nextContext, result);
 }
 
-static inline Element* parentOrShadowHostButDisallowEscapingUserAgentShadowTree(const Element& element)
-{
-    ContainerNode* parent = element.parentOrShadowHostNode();
-    if (!parent)
-        return nullptr;
-    if (parent->isShadowRoot())
-        return (toShadowRoot(parent)->type() == ShadowRoot::UserAgentShadowRoot) ? nullptr : toShadowRoot(parent)->host();
-    if (!parent->isElementNode())
-        return nullptr;
-    return toElement(parent);
-}
-
 static inline bool isOpenShadowRoot(const Node* node)
 {
     return node && node->isShadowRoot() && toShadowRoot(node)->type() == ShadowRoot::OpenShadowRoot;
 }
 
 SelectorChecker::Match SelectorChecker::matchForPseudoShadow(const SelectorCheckingContext& context, const ContainerNode* node, MatchResult& result) const
 {
     if (!isOpenShadowRoot(node))
         return SelectorFailsCompletely;
     if (!context.previousElement)
@@ skipping 98 matching lines @@
             if (!shadowHost)
                 return SelectorFailsCompletely;
             nextContext.element = shadowHost;
             nextContext.isSubSelector = false;
             nextContext.inRightmostCompound = false;
             return matchSelector(nextContext, result);
         }
 
     case CSSSelector::ShadowDeep:
         {
+            if (ShadowRoot* root = context.element->containingShadowRoot()) {
+                if (root->type() == ShadowRoot::UserAgentShadowRoot)
+                    return SelectorFailsCompletely;
+            }
+
             if (context.selector->relationIsAffectedByPseudoContent()) {
-                for (Element* element = context.element; element; element = parentOrShadowHostButDisallowEscapingUserAgentShadowTree(*element)) {
+                for (Element* element = context.element; element; element = element->parentOrShadowHostElement()) {
                     if (matchForShadowDistributed(nextContext, *element, result) == SelectorMatches)
                         return SelectorMatches;
                 }
                 return SelectorFailsCompletely;
             }
 
             nextContext.isSubSelector = false;
             nextContext.inRightmostCompound = false;
-            for (nextContext.element = parentOrShadowHostButDisallowEscapingUserAgentShadowTree(*context.element); nextContext.element; nextContext.element = parentOrShadowHostButDisallowEscapingUserAgentShadowTree(*nextContext.element)) {
+            for (nextContext.element = context.element->parentOrShadowHostElement(); nextContext.element; nextContext.element = nextContext.element->parentOrShadowHostElement()) {
                 Match match = matchSelector(nextContext, result);
                 if (match == SelectorMatches || match == SelectorFailsCompletely)
                     return match;
                 if (nextSelectorExceedsScope(nextContext))
                     return SelectorFailsCompletely;
             }
             return SelectorFailsCompletely;
         }
 
     case CSSSelector::SubSelector:
@@ skipping 733 matching lines @@
 }
 
 bool SelectorChecker::matchesFocusPseudoClass(const Element& element)
 {
     if (InspectorInstrumentation::forcePseudoState(const_cast<Element*>(&element), CSSSelector::PseudoFocus))
         return true;
     return element.focused() && isFrameFocused(element);
 }
 
 }