parserInsertBefore and parserRemoveChild should check newChild for a parent.

Source/core/html/parser/HTMLConstructionSite.cpp

 /*
  * Copyright (C) 2010 Google, Inc. All Rights Reserved.
  * Copyright (C) 2011 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 84 matching lines @@
 static inline bool isAllWhitespace(const String& string)
 {
     return string.isAllSpecialCharacters<isHTMLSpace<UChar>>();
 }
 
 static inline void insert(HTMLConstructionSiteTask& task)
 {
     if (isHTMLTemplateElement(*task.parent))
         task.parent = toHTMLTemplateElement(task.parent.get())->content();
 
-    if (ContainerNode* parent = task.child->parentNode())
-        parent->parserRemoveChild(*task.child);
-
     if (task.nextChild)
         task.parent->parserInsertBefore(task.child.get(), *task.nextChild);
     else
         task.parent->parserAppendChild(task.child.get());
 }
 
 static inline void executeInsertTask(HTMLConstructionSiteTask& task)
 {
     ASSERT(task.operation == HTMLConstructionSiteTask::Insert);
 
@@ skipping 25 matching lines @@
         }
     }
 
     insert(task);
 }
 
 static inline void executeReparentTask(HTMLConstructionSiteTask& task)
 {
     ASSERT(task.operation == HTMLConstructionSiteTask::Reparent);
 
-    if (ContainerNode* parent = task.child->parentNode())
-        parent->parserRemoveChild(*task.child);
-
     task.parent->parserAppendChild(task.child);
 }
 
 static inline void executeInsertAlreadyParsedChildTask(HTMLConstructionSiteTask& task)
 {
     ASSERT(task.operation == HTMLConstructionSiteTask::InsertAlreadyParsedChild);
 
     insert(task);
 }
 
@@ skipping 713 matching lines @@
 }
 
 DEFINE_TRACE(HTMLConstructionSite::PendingText)
 {
     visitor->trace(parent);
     visitor->trace(nextChild);
 }
 
 
 }