Add Traversal<*Element>::firstAncestor() API

Source/core/accessibility/AXNodeObject.cpp

 /*
 * Copyright (C) 2012, Google 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
@@ skipping 1449 matching lines @@
 
 HTMLLabelElement* AXNodeObject::labelElementContainer() const
 {
     if (!node())
         return 0;
 
     // the control element should not be considered part of the label
     if (isControl())
         return 0;
 
-    // find if this has a parent that is a label
-    for (Node* parentNode = node(); parentNode; parentNode = parentNode->parentNode()) {
-        if (isHTMLLabelElement(*parentNode))
-            return toHTMLLabelElement(parentNode);
-    }
-
-    return 0;
+    // find if this has a ancestor that is a label
+    if (isHTMLLabelElement(*node()))
+        return toHTMLLabelElement(node());
+    return Traversal<HTMLLabelElement>::firstAncestor(*node());
 }
 
 void AXNodeObject::setFocused(bool on)
 {
     if (!canSetFocusAttribute())
         return;
 
     Document* document = this->document();
     if (!on) {
         document->setFocusedElement(nullptr);
@@ skipping 185 matching lines @@
     float range = maxValueForRange() - minValueForRange();
     float value = valueForRange();
 
     value += range * (percentChange / 100);
     setValue(String::number(value));
 
     axObjectCache()->postNotification(node(), AXObjectCache::AXValueChanged, true);
 }
 
 } // namespace WebCore