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

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

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * 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.
@@ skipping 726 matching lines @@
     virtual InvalidState getInvalidState() const { return InvalidStateUndefined; }
     // Only used when invalidState() returns InvalidStateOther.
     virtual String ariaInvalidValue() const { return String(); }
     virtual String valueDescription() const { return String(); }
     virtual float valueForRange() const { return 0.0f; }
     virtual float maxValueForRange() const { return 0.0f; }
     virtual float minValueForRange() const { return 0.0f; }
     virtual String stringValue() const { return String(); }
 
     // ARIA attributes.
-    virtual AXObject* activeDescendant() const { return nullptr; }
+    virtual AXObject* activeDescendant() { return nullptr; }
     virtual String ariaAutoComplete() const { return String(); }
     virtual String ariaDescribedByAttribute() const { return String(); }
     virtual void ariaFlowToElements(AXObjectVector&) const { }
     virtual void ariaControlsElements(AXObjectVector&) const { }
     virtual void ariaOwnsElements(AXObjectVector& owns) const { }
     virtual void ariaDescribedbyElements(AXObjectVector&) const { }
     virtual void ariaLabelledbyElements(AXObjectVector&) const { }
     virtual bool ariaHasPopup() const { return false; }
     virtual bool isEditable() const { return false; }
     bool isMultiline() const;
@@ skipping 200 matching lines @@
 #define DEFINE_AX_OBJECT_TYPE_CASTS(thisType, predicate) \
     DEFINE_TYPE_CASTS(thisType, AXObject, object, object->predicate, object.predicate)
 
 } // namespace blink
 
 WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(blink::IgnoredReason);
 WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(blink::NameSource);
 WTF_ALLOW_INIT_WITH_MEM_FUNCTIONS(blink::DescriptionSource);
 
 #endif // AXObject_h