Use new is*Element() helper functions in CSS code

Source/core/css/StyleInvalidationAnalysis.cpp

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 139 matching lines @@
     const WillBeHeapVector<RefPtrWillBeMember<StyleRuleImport> >& importRules = styleSheetContents->importRules();
     for (unsigned i = 0; i < importRules.size(); ++i) {
         if (!importRules[i]->styleSheet())
             continue;
         analyzeStyleSheet(importRules[i]->styleSheet());
         if (m_dirtiesAllStyle)
             return;
     }
     if (styleSheetContents->hasSingleOwnerNode()) {
         Node* ownerNode = styleSheetContents->singleOwnerNode();
-        if (ownerNode && ownerNode->hasTagName(HTMLNames::styleTag) && toHTMLStyleElement(ownerNode)->isRegisteredAsScoped()) {
+        if (isHTMLStyleElement(ownerNode) && toHTMLStyleElement(*ownerNode).isRegisteredAsScoped()) {
             m_scopingNodes.append(determineScopingNodeForStyleScoped(toHTMLStyleElement(ownerNode), styleSheetContents));
             return;
         }
     }
 
     const WillBeHeapVector<RefPtrWillBeMember<StyleRuleBase> >& rules = styleSheetContents->childRules();
     for (unsigned i = 0; i < rules.size(); i++) {
         StyleRuleBase* rule = rules[i].get();
         if (!rule->isStyleRule()) {
             if (ruleAdditionMightRequireDocumentStyleRecalc(rule)) {
@@ skipping 41 matching lines @@
             element->setNeedsStyleRecalc(SubtreeStyleChange);
             // The whole subtree is now invalidated, we can skip to the next sibling.
             element = ElementTraversal::nextSkippingChildren(*element);
             continue;
         }
         element = ElementTraversal::next(*element);
     }
 }
 
 }