Avoid calling slower Node::firstChild() / Node::lastChild() when possible

Source/core/editing/CompositeEditCommand.h

 /*
  * Copyright (C) 2005, 2006, 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 128 matching lines @@
 
     void deleteInsignificantText(PassRefPtrWillBeRawPtr<Text>, unsigned start, unsigned end);
     void deleteInsignificantText(const Position& start, const Position& end);
     void deleteInsignificantTextDownstream(const Position&);
 
     PassRefPtrWillBeRawPtr<Node> appendBlockPlaceholder(PassRefPtrWillBeRawPtr<Element>);
     PassRefPtrWillBeRawPtr<Node> insertBlockPlaceholder(const Position&);
     PassRefPtrWillBeRawPtr<Node> addBlockPlaceholderIfNeeded(Element*);
     void removePlaceholderAt(const Position&);
 
-    PassRefPtrWillBeRawPtr<Node> insertNewDefaultParagraphElementAt(const Position&);
+    PassRefPtrWillBeRawPtr<Element> insertNewDefaultParagraphElementAt(const Position&);
 
-    PassRefPtrWillBeRawPtr<Node> moveParagraphContentsToNewBlockIfNecessary(const Position&);
+    PassRefPtrWillBeRawPtr<Element> moveParagraphContentsToNewBlockIfNecessary(const Position&);
 
     void pushAnchorElementDown(Node*);
 
     // FIXME: preserveSelection and preserveStyle should be enums
     void moveParagraph(const VisiblePosition&, const VisiblePosition&, const VisiblePosition&, bool preserveSelection = false, bool preserveStyle = true, Node* constrainingAncestor = 0);
     void moveParagraphs(const VisiblePosition&, const VisiblePosition&, const VisiblePosition&, bool preserveSelection = false, bool preserveStyle = true, Node* constrainingAncestor = 0);
     void moveParagraphWithClones(const VisiblePosition& startOfParagraphToMove, const VisiblePosition& endOfParagraphToMove, Element* blockElement, Node* outerNode);
     void cloneParagraphUnderNewElement(const Position& start, const Position& end, Node* outerNode, Element* blockElement);
     void cleanupAfterDeletion(VisiblePosition destination = VisiblePosition());
 
@@ skipping 10 matching lines @@
     virtual bool isCompositeEditCommand() const OVERRIDE FINAL { return true; }
 
     RefPtrWillBeMember<EditCommandComposition> m_composition;
 };
 
 DEFINE_TYPE_CASTS(CompositeEditCommand, EditCommand, command, command->isCompositeEditCommand(), command.isCompositeEditCommand());
 
 } // namespace WebCore
 
 #endif // CompositeEditCommand_h