Fix leaking AXNodeObjects when sub document detaches

third_party/WebKit/Source/modules/accessibility/AXTableHeaderContainer.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 51 matching lines @@
         return false;
 
     if (ignoredReasons)
         m_parent->computeAccessibilityIsIgnored(ignoredReasons);
 
     return true;
 }
 
 void AXTableHeaderContainer::addChildren()
 {
+    ASSERT(!isDetached());
     ASSERT(!m_haveChildren);
 
     m_haveChildren = true;
     if (!m_parent || !m_parent->isAXTable())
         return;
 
     toAXTable(m_parent)->columnHeaders(m_children);
 
     unsigned length = m_children.size();
     for (unsigned k = 0; k < length; ++k)
         m_headerRect.unite(m_children[k]->elementRect());
 }
 
 } // namespace blink