Make AttachBehavior a required argument.

Source/core/editing/CompositeEditCommand.cpp

Index: Source/core/editing/CompositeEditCommand.cpp
diff --git a/Source/core/editing/CompositeEditCommand.cpp b/Source/core/editing/CompositeEditCommand.cpp
index 4ed9df82e9454079420ecb12c748900de7d1d995..dfe6e42efe0cdd94b454ef9488fb2e5988232928 100644
--- a/Source/core/editing/CompositeEditCommand.cpp
+++ b/Source/core/editing/CompositeEditCommand.cpp
@@ -890,7 +890,7 @@ void CompositeEditCommand::removePlaceholderAt(const Position& p)
 PassRefPtr<Node> CompositeEditCommand::insertNewDefaultParagraphElementAt(const Position& position)
 {
     RefPtr<Element> paragraphElement = createDefaultParagraphElement(document());
-    paragraphElement->appendChild(createBreakElement(document()), IGNORE_EXCEPTION);
+    paragraphElement->appendChild(createBreakElement(document()), IGNORE_EXCEPTION, DeprecatedAttachNow);
     insertNodeAt(paragraphElement, position);
     return paragraphElement.release();
 }