Simplify SelectorChecker's parentElement() function

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 63 matching lines @@
         return false;
 
     if (element->shadowPseudoId() != selector.value())
         return false;
 
     return true;
 }
 
 static Element* parentElement(const SelectorChecker::SelectorCheckingContext& context)
 {
-    // If context.scope is a shadow root, we should walk up to its shadow host.
-    if (context.scope && context.scope == context.element->containingShadowRoot())
+    // - If context.scope is a shadow root, we should walk up to its shadow host.
+    // - If context.scope is some element in some shadow tree and querySelector initialized the context,
+    //   e.g. shadowRoot.querySelector(':host *'),
+    //   (a) context.element has the same treescope as context.scope, need to walk up to its shadow host.
+    //   (b) Otherwise, should not walk up from a shadow root to a shadow host.
+    if (context.scope && (context.scope == context.element->containingShadowRoot() || context.scope->treeScope() == context.element->treeScope()))
         return context.element->parentOrShadowHostElement();
-
-    // If context.scope is some element in some shadow tree and querySelector initialized the context,
-    // e.g. shadowRoot.querySelector(':host *'),
-    // (a) context.element has the same treescope as context.scope, need to walk up to its shadow host.
-    // (b) Otherwise, should not walk up from a shadow root to a shadow host.
-    if (context.scope && context.scope->treeScope() == context.element->treeScope())
-        return context.element->parentOrShadowHostElement();
-
     return context.element->parentElement();
 }
 
 static bool scopeContainsLastMatchedElement(const SelectorChecker::SelectorCheckingContext& context)
 {
     if (!(context.contextFlags & SelectorChecker::ScopeContainsLastMatchedElement))
         return true;
 
     ASSERT(context.scope);
     if (context.scope->treeScope() == context.element->treeScope())
@@ skipping 1024 matching lines @@
     return isHTMLOptionElement(element) && toHTMLOptionElement(element).spatialNavigationFocused() && isFrameFocused(element);
 }
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const DOMSiblingTraversalStrategy&, MatchResult*) const;
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const ShadowDOMSiblingTraversalStrategy&, MatchResult*) const;
 
 }