DOM: Remove standard-violating optimizations in appendChild, insertBefore, and replaceChild.

third_party/WebKit/Source/core/dom/Range.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 899 matching lines @@
       // include the inserted nodes.
       Node* firstChild = (newNodeType == Node::kDocumentFragmentNode)
                              ? toDocumentFragment(newNode)->firstChild()
                              : newNode;
       DCHECK(firstChild);
       m_start.setToBeforeChild(*firstChild);
       return;
     }
 
     container = m_start.container();
-    container->insertBefore(
-        newNode, NodeTraversal::childAt(*container, m_start.offset()),
-        exceptionState);
-    if (exceptionState.hadException())
-      return;
+    Node* referenceNode = NodeTraversal::childAt(*container, m_start.offset());
+    // TODO(tkent): The following check must be unnecessary if we follow the
+    // algorithm defined in the specification.
+    // https://dom.spec.whatwg.org/#concept-range-insert
+    if (newNode != referenceNode) {
+      container->insertBefore(newNode, referenceNode, exceptionState);
+      if (exceptionState.hadException())
+        return;
+    }
 
     // Note that m_start.offset() may have changed as a result of
     // container->insertBefore, when the node we are inserting comes before the
     // range in the same container.
     if (collapsed && numNewChildren)
       m_end.set(m_start.container(), m_start.offset() + numNewChildren,
                 lastChild);
   }
 }
 
@@ skipping 781 matching lines @@
                      .data()
               << "start offset: " << range->startOffset()
               << ", end offset: " << range->endOffset();
   } else {
     LOG(INFO) << "Cannot show tree if range is null, or if boundary points are "
                  "invalid.";
   }
 }
 
 #endif