Fix leaking AXNodeObjects when sub document detaches

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

 /*
  * Copyright (C) 2008 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 43 matching lines @@
 HTMLMapElement* AXImageMapLink::mapElement() const
 {
     HTMLAreaElement* area = areaElement();
     if (!area)
         return nullptr;
     return Traversal<HTMLMapElement>::firstAncestor(*area);
 }
 
 AXObject* AXImageMapLink::computeParent() const
 {
+    ASSERT(!isDetached());
     if (m_parent)
         return m_parent;
 
     if (!mapElement())
         return nullptr;
 
     return axObjectCache().getOrCreate(mapElement()->layoutObject());
 }
 
 AccessibilityRole AXImageMapLink::roleValue() const
@@ skipping 70 matching lines @@
 
     return area->computeRect(layoutObject);
 }
 
 DEFINE_TRACE(AXImageMapLink)
 {
     AXNodeObject::trace(visitor);
 }
 
 } // namespace blink