Use ContainerNode::hasChildren() instead of firstChild() in conditionals

Source/core/editing/SimplifyMarkupCommand.cpp

 /*
  * Copyright (C) 2012 Apple Computer, 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 31 matching lines @@
 void SimplifyMarkupCommand::doApply()
 {
     Node* rootNode = m_firstNode->parentNode();
     WillBeHeapVector<RefPtrWillBeMember<Node> > nodesToRemove;
 
     // Walk through the inserted nodes, to see if there are elements that could be removed
     // without affecting the style. The goal is to produce leaner markup even when starting
     // from a verbose fragment.
     // We look at inline elements as well as non top level divs that don't have attributes.
     for (Node* node = m_firstNode.get(); node && node != m_nodeAfterLast; node = NodeTraversal::next(*node)) {
-        if (node->firstChild() || (node->isTextNode() && node->nextSibling()))
+        if (node->hasChildren() || (node->isTextNode() && node->nextSibling()))
             continue;
 
         Node* startingNode = node->parentNode();
         if (!startingNode)
             continue;
         RenderStyle* startingStyle = startingNode->renderStyle();
         if (!startingStyle)
             continue;
         Node* currentNode = startingNode;
         Node* topNodeWithStartingStyle = 0;
@@ skipping 59 matching lines @@
 }
 
 void SimplifyMarkupCommand::trace(Visitor* visitor)
 {
     visitor->trace(m_firstNode);
     visitor->trace(m_nodeAfterLast);
     CompositeEditCommand::trace(visitor);
 }
 
 } // namespace blink