Make several DOMImplementation API arguments mandatory

LayoutTests/fast/dom/DOMImplementation/script-tests/createDocument-namespace-err.js

 description("createDocument tests modeled after createElementNS tests from mozilla which were attached to webkit bug 16833");
 
 // document.implementation.createDocument() should throw the same set of errors
 // as document.createElementNS()
 // http://www.w3.org/TR/DOM-Level-3-Core/core.html#Level-2-Core-DOM-createDocument
 // Thus we copied these test cases from:
 // LayoutTests/fast/dom/Document/resources/createDocument-namespace-err.js
 
 function assert(c, m)
 {
@@ skipping 119 matching lines @@
             msg += "; " + test.message;
         try {
             doc[createFunctionName].apply(doc, argsWithExtraLastNull);
             assert(!("code" in test), msg);
         } catch (e) {
             assertEquals(e.code, test.code || "expected no exception", msg);
         }
     }
 }
 
-// Moz throws a "Not enough arguments" exception in these, we don't:
-shouldBeEqualToString("document.implementation.createDocument().toString()", "[object Document]");
-shouldBeEqualToString("document.implementation.createDocument(\"http://www.example.com\").toString()", "[object Document]");
+shouldThrow("document.implementation.createDocument()", "'TypeError: Not enough arguments'");
+shouldThrow("document.implementation.createDocument(\"http://www.example.com\")", "'TypeError: Not enough arguments'");
 
 runNSTests(allNSTests, document.implementation, "createDocument");