Adding ASSERT for RuntimeEnabled feature XSLT

Source/core/xml/XSLTExtensions.cpp

Index: Source/core/xml/XSLTExtensions.cpp
diff --git a/Source/core/xml/XSLTExtensions.cpp b/Source/core/xml/XSLTExtensions.cpp
index eea94179e3cf69c2e35da5ab80d5bf2d84fe6f29..064d609955bae64219715403b8366c86fb3e5b1a 100644
--- a/Source/core/xml/XSLTExtensions.cpp
+++ b/Source/core/xml/XSLTExtensions.cpp
@@ -27,6 +27,8 @@
 #include "config.h"
 
 #include "core/xml/XSLTExtensions.h"
+#include "RuntimeEnabledFeatures.h"
+#include "wtf/Assertions.h"
 
 #include <libxml/xpathInternals.h>
 
@@ -70,6 +72,7 @@ static void exsltNodeSetFunction(xmlXPathParserContextPtr ctxt, int nargs)
 
 void registerXSLTExtensions(xsltTransformContextPtr ctxt)
 {
+    ASSERT(RuntimeEnabledFeatures::xsltEnabled());
     xsltRegisterExtFunction(ctxt, (const xmlChar*)"node-set", (const xmlChar*)"http://exslt.org/common", exsltNodeSetFunction);
 }