Adding ASSERT for RuntimeEnabled feature XSLT

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:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
  * NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CON-
  * NECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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 #include "config.h"
 
 #include "core/xml/XSLTExtensions.h"
+#include "RuntimeEnabledFeatures.h"
+#include "wtf/Assertions.h"
 
 #include <libxml/xpathInternals.h>
 
 #include <libxslt/extensions.h>
 #include <libxslt/extra.h>
 #include <libxslt/xsltutils.h>
 
 namespace WebCore {
 
 // FIXME: This code is taken from libexslt 1.1.11; should sync with newer versions.
@@ skipping 23 matching lines @@
         ret->type = XPATH_NODESET;
 
     if (strval != NULL)
         xmlFree(strval);
 
     valuePush(ctxt, ret);
 }
 
 void registerXSLTExtensions(xsltTransformContextPtr ctxt)
 {
+    ASSERT(RuntimeEnabledFeatures::xsltEnabled());
     xsltRegisterExtFunction(ctxt, (const xmlChar*)"node-set", (const xmlChar*)"http://exslt.org/common", exsltNodeSetFunction);
 }
 
 } // namespace WebCore