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

Source/core/editing/TypingCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 2007, 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 368 matching lines @@
         return;
     }
 
     applyCommandToComposite(BreakBlockquoteCommand::create(document()));
     typingAddedToOpenCommand(InsertParagraphSeparatorInQuotedContent);
 }
 
 bool TypingCommand::makeEditableRootEmpty()
 {
     Element* root = endingSelection().rootEditableElement();
-    if (!root || !root->firstChild())
+    if (!root || !root->hasChildren())
         return false;
 
     if (root->firstChild() == root->lastChild()) {
         Element* firstElementChild = ElementTraversal::firstWithin(*root);
         if (isHTMLBRElement(firstElementChild)) {
             // If there is a single child and it could be a placeholder, leave it alone.
             if (root->renderer() && root->renderer()->isRenderBlockFlow())
                 return false;
         }
     }
@@ skipping 225 matching lines @@
     ASSERT_NOT_REACHED();
     m_preservesTypingStyle = false;
 }
 
 bool TypingCommand::isTypingCommand() const
 {
     return true;
 }
 
 } // namespace blink