Reland of Uses the activedescendant_changed event received from Blink to fire the right focus event

third_party/WebKit/Source/modules/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 127 matching lines @@
 
     float value = valueForRange();
     float step = stepValueForRange();
 
     value += increase ? step : -step;
 
     setValue(String::number(value));
     axObjectCache().postNotification(getNode(), AXObjectCacheImpl::AXValueChanged);
 }
 
-AXObject* AXNodeObject::activeDescendant() const
+AXObject* AXNodeObject::activeDescendant()
 {
     if (!getNode() || !getNode()->isElementNode())
         return nullptr;
 
     const AtomicString& activeDescendantAttr = getAttribute(aria_activedescendantAttr);
     if (activeDescendantAttr.isNull() || activeDescendantAttr.isEmpty())
         return nullptr;
 
     Element* element = toElement(getNode());
     Element* descendant = element->treeScope().getElementById(activeDescendantAttr);
@@ skipping 2688 matching lines @@
     return placeholder;
 }
 
 DEFINE_TRACE(AXNodeObject)
 {
     visitor->trace(m_node);
     AXObject::trace(visitor);
 }
 
 } // namespace blink