Fix leaking AXNodeObjects when sub document detaches

third_party/WebKit/Source/modules/accessibility/AXTable.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 341 matching lines @@
     m_columns.clear();
 
     if (m_headerContainer) {
         m_headerContainer->detachFromParent();
         m_headerContainer = nullptr;
     }
 }
 
 void AXTable::addChildren()
 {
+    ASSERT(!isDetached());
     if (!isAXTable()) {
         AXLayoutObject::addChildren();
         return;
     }
 
     ASSERT(!m_haveChildren);
 
     m_haveChildren = true;
     if (!m_layoutObject || !m_layoutObject->isTable())
         return;
@@ skipping 222 matching lines @@
 
 DEFINE_TRACE(AXTable)
 {
     visitor->trace(m_rows);
     visitor->trace(m_columns);
     visitor->trace(m_headerContainer);
     AXLayoutObject::trace(visitor);
 }
 
 } // namespace blink