Make AttachBehavior a required argument.

Source/core/editing/MergeIdenticalElementsCommand.cpp

Index: Source/core/editing/MergeIdenticalElementsCommand.cpp
diff --git a/Source/core/editing/MergeIdenticalElementsCommand.cpp b/Source/core/editing/MergeIdenticalElementsCommand.cpp
index e94a7fb647f621eb76759a1040235ce261c92fd1..6d8ccfc6cc01b4b1a8eed73da72bbda2ddd2c375 100644
--- a/Source/core/editing/MergeIdenticalElementsCommand.cpp
+++ b/Source/core/editing/MergeIdenticalElementsCommand.cpp
@@ -55,7 +55,7 @@ void MergeIdenticalElementsCommand::doApply()
 
     size_t size = children.size();
     for (size_t i = 0; i < size; ++i)
-        m_element2->insertBefore(children[i].release(), m_atChild.get(), IGNORE_EXCEPTION);
+        m_element2->insertBefore(children[i].release(), m_atChild.get(), IGNORE_EXCEPTION, DeprecatedAttachNow);
 
     m_element1->remove(IGNORE_EXCEPTION);
 }
@@ -73,7 +73,7 @@ void MergeIdenticalElementsCommand::doUnapply()
 
     TrackExceptionState es;
 
-    parent->insertBefore(m_element1.get(), m_element2.get(), es);
+    parent->insertBefore(m_element1.get(), m_element2.get(), es, DeprecatedAttachNow);
     if (es.hadException())
         return;
 
@@ -83,7 +83,7 @@ void MergeIdenticalElementsCommand::doUnapply()
 
     size_t size = children.size();
     for (size_t i = 0; i < size; ++i)
-        m_element1->appendChild(children[i].release(), es);
+        m_element1->appendChild(children[i].release(), es, DeprecatedAttachNow);
 }
 
 #ifndef NDEBUG