Use new is*Element() helper functions more in editing code

Source/core/editing/FormatBlockCommand.cpp

 /*
  * Copyright (C) 2006 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 138 matching lines @@
     }
     return blockTags.contains(tagName);
 }
 
 Node* enclosingBlockToSplitTreeTo(Node* startNode)
 {
     Node* lastBlock = startNode;
     for (Node* n = startNode; n; n = n->parentNode()) {
         if (!n->rendererIsEditable())
             return lastBlock;
-        if (isTableCell(n) || n->hasTagName(bodyTag) || !n->parentNode() || !n->parentNode()->rendererIsEditable() || isElementForFormatBlock(n))
+        if (isTableCell(n) || isHTMLBodyElement(*n) || !n->parentNode() || !n->parentNode()->rendererIsEditable() || isElementForFormatBlock(n))
             return n;
         if (isBlock(n))
             lastBlock = n;
         if (isListElement(n))
             return n->parentNode()->rendererIsEditable() ? n->parentNode() : n;
     }
     return lastBlock;
 }
 
 }