Enable accessible name of a control to include multiple <label> elements.

third_party/WebKit/Source/modules/accessibility/AXObject.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 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
@@ skipping 730 matching lines @@
     AXObjectSet visited;
     AXNameFrom tmpNameFrom;
     AXRelatedObjectVector tmpRelatedObjects;
     String text = textAlternative(false, false, visited, tmpNameFrom, &tmpRelatedObjects, nameSources);
     text = text.simplifyWhiteSpace(isHTMLSpace<UChar>);
     return text;
 }
 
 String AXObject::recursiveTextAlternative(const AXObject& axObj, bool inAriaLabelledByTraversal, AXObjectSet& visited)
 {
+    if (visited.contains(&axObj) && !inAriaLabelledByTraversal)
+        return String();
+
     AXNameFrom tmpNameFrom;
     return axObj.textAlternative(true, inAriaLabelledByTraversal, visited, tmpNameFrom, nullptr, nullptr);
 }
 
 bool AXObject::isHiddenForTextAlternativeCalculation() const
 {
     if (equalIgnoringCase(getAttribute(aria_hiddenAttr), "false"))
         return false;
 
     if (getLayoutObject())
@@ skipping 970 matching lines @@
 
 DEFINE_TRACE(AXObject)
 {
     visitor->trace(m_children);
     visitor->trace(m_parent);
     visitor->trace(m_cachedLiveRegionRoot);
     visitor->trace(m_axObjectCache);
 }
 
 } // namespace blink