node-set($x), when $x is empty, should not halt XSLT processing

third_party/WebKit/Source/core/xml/XSLTExtensions.cpp

 /**
  * Copyright (C) 2001-2002 Thomas Broyer, Charlie Bozeman and Daniel Veillard.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is fur-
  * nished to do so, subject to the following conditions:
@@ skipping 34 matching lines @@
   if (nargs != 1) {
     xmlXPathSetArityError(ctxt);
     return;
   }
 
   if (xmlXPathStackIsNodeSet(ctxt)) {
     xsltFunctionNodeSet(ctxt, nargs);
     return;
   }
 
+  // node-set can also take a string and turn it into a singleton node
+  // set with one text node. This may null-deref if allocating the
+  // document, text node, etc. fails; that behavior is expected.
+
+  // Create a document to hold the text node result.
+  xsltTransformContextPtr tctxt = xsltXPathGetTransformContext(ctxt);
+  xmlDocPtr fragment = xsltCreateRVT(tctxt);
+  xsltRegisterLocalRVT(tctxt, fragment);
+
+  // Create the text node and wrap it in a result set.
   strval = xmlXPathPopString(ctxt);
-  retNode = xmlNewDocText(0, strval);
-  ret = xmlXPathNewValueTree(retNode);
-
-  // FIXME: It might be helpful to push any errors from xmlXPathNewValueTree
-  // up to the Javascript Console.
-  if (ret)
-    ret->type = XPATH_NODESET;
+  retNode = xmlNewDocText(fragment, strval);
+  xmlAddChild(reinterpret_cast<xmlNodePtr>(fragment), retNode);
+  ret = xmlXPathNewNodeSet(retNode);
+  CHECK(ret);
 
   if (strval)
     xmlFree(strval);
 
   valuePush(ctxt, ret);
 }
 
 void registerXSLTExtensions(xsltTransformContextPtr ctxt) {
   DCHECK(RuntimeEnabledFeatures::xsltEnabled());
   xsltRegisterExtFunction(ctxt, (const xmlChar*)"node-set",
                           (const xmlChar*)"http://exslt.org/common",
                           exsltNodeSetFunction);
 }
 
 }  // namespace blink