Use ElementTraversal API in ContainerNode::checkForChildrenAdjacentRuleChanges()

Source/core/dom/ContainerNode.cpp

Index: Source/core/dom/ContainerNode.cpp
diff --git a/Source/core/dom/ContainerNode.cpp b/Source/core/dom/ContainerNode.cpp
index 19d79ab8704453a72d111d5a649e1d7f66f26f27..fed648dbb0002f7a4a4f906e439df3f33500c162 100644
--- a/Source/core/dom/ContainerNode.cpp
+++ b/Source/core/dom/ContainerNode.cpp
@@ -1116,20 +1116,16 @@ void ContainerNode::checkForChildrenAdjacentRuleChanges()
     bool forceCheckOfAnyElementSibling = false;
     Document& document = this->document();
 
-    for (Node* child = firstChild(); child; child = child->nextSibling()) {
-        if (!child->isElementNode())
-            continue;
-        Element* element = toElement(child);
-        bool childRulesChanged = element->needsStyleRecalc() && element->styleChangeType() >= SubtreeStyleChange;
+    for (Element* child = ElementTraversal::firstChild(*this); child; child = ElementTraversal::nextSibling(*child)) {
+        bool childRulesChanged = child->needsStyleRecalc() && child->styleChangeType() >= SubtreeStyleChange;
 
         if (forceCheckOfNextElementCount || forceCheckOfAnyElementSibling)
-            element->setNeedsStyleRecalc(SubtreeStyleChange);
-
-        if (forceCheckOfNextElementCount)
-            forceCheckOfNextElementCount--;
+            child->setNeedsStyleRecalc(SubtreeStyleChange);
 
         if (childRulesChanged && hasDirectAdjacentRules)
             forceCheckOfNextElementCount = document.styleEngine()->maxDirectAdjacentSelectors();
+        else if (forceCheckOfNextElementCount)
+            --forceCheckOfNextElementCount;
 
         forceCheckOfAnyElementSibling = forceCheckOfAnyElementSibling || (childRulesChanged && hasIndirectAdjacentRules);
     }