CharacterData.substringData() arguments should be mandatory

LayoutTests/fast/dom/script-tests/non-numeric-values-numeric-parameters.js

 description(
 'This tests the behavior of non-numeric values in contexts where the DOM has a numeric parameter.'
 );
 
 function nonNumericPolicy(template)
 {
     var x = 0;
     try {
         eval(template);
     } catch (e) {
@@ skipping 168 matching lines @@
 {
     var table = document.createElement("table");
     var row = table.insertRow(0);
     row.insertCell(0);
     return row;
 }
 
 // CharacterData
 
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").substringData(x, 0)')", "'any type allowed'");
-shouldBe("nonNumericPolicy('document.createTextNode(\"a\").substringData(0, x)')", "'any type allowed'");
+shouldBe("nonNumericPolicy('document.createTextNode(\"a\").substringData(0, x)')", "'any type allowed (but not omitted)'");
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").insertData(x, \"b\")')", "'any type allowed'");
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").deleteData(x, 0)')", "'any type allowed'");
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").deleteData(0, x)')", "'any type allowed (but not omitted)'");
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").replaceData(x, 0, \"b\")')", "'any type allowed'");
 shouldBe("nonNumericPolicy('document.createTextNode(\"a\").replaceData(0, x, \"b\")')", "'any type allowed'");
 
 // CSSMediaRule
 
 shouldBe("nonNumericPolicy('createCSSMediaRule().insertRule(ruleText, x)')", "'any type allowed'");
 shouldBe("nonNumericPolicy('createCSSMediaRule().deleteRule(x)')", "'any type allowed'");
@@ skipping 440 matching lines @@
 ../../../../WebCore/svg/SVGSVGElement.idl:                 attribute float currentScale
 
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double a;
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double b;
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double c;
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double d;
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double e;
 ../../../../WebCore/svg/SVGMatrix.idl:        attribute double f;
 
 */