Do not special case null for URLUtils attributes

LayoutTests/fast/dom/HTMLAnchorElement/script-tests/set-href-attribute-hostname.js

 description('Test setting the hostname attribute of the URL in HTMLAnchorElement.');
 
 var a = document.createElement('a');
 
 debug("Basic test");
 a.href = "https://www.mydomain.com:8080/path/";
 a.hostname = "www.otherdomain.com";
 shouldBe("a.href", "'https://www.otherdomain.com:8080/path/'");
 
 // IE8 throws an exception "The URL is invalid".
 try {
 debug("Extra slashes before hostname");
 a.href = "https://www.mydomain.com:8080/path/";
 a.hostname = "//www.otherdomain.com";
 shouldBe("a.href", "'https://www.otherdomain.com:8080/path/'");
 } catch(e) {
 debug("Exception: " + e.description);
 }
 
 // Firefox 3.5.2 does not allow setting the host to foo: protocol
 debug("Set hostname to URL with foo: protocol");
 a.href = "foo://www.mydomain.com/path/";
 a.hostname = "www.otherdomain.com";
 shouldBe("a.href", "'foo://www.otherdomain.com/path/'");
 
-// IE8 converts null to "null", which is not the right thing to do.
-// Firefox 3.5.2 allows setting the hostname to null, which is wrong per
-// http://dev.w3.org/html5/spec/infrastructure.html#url-decomposition-idl-attributes .
 debug("Set hostname to null");
 a.href = "https://www.mydomain.com:8080/path/";
 a.hostname = null;
-shouldBe("a.href", "'https://www.mydomain.com:8080/path/'");
+shouldBe("a.href", "'https://null:8080/path/'");
 
 // Both IE8 and Firefox 3.5.2 allow setting the host to empty string, against the spec at
 // http://dev.w3.org/html5/spec/infrastructure.html#url-decomposition-idl-attributes .
 // Since both do that in a buggy way, WebKit should not follow either one of them.
 debug("Set hostname to empty string");
 a.href = "https://www.mydomain.com:8080/path/";
 a.hostname = "";
 shouldBe("a.href", "'https://www.mydomain.com:8080/path/'");
 
 // IE8 fails to process really: protocol.
@@ skipping 18 matching lines @@
 a.hostname= "a";
 shouldBe("a.href", "'c:/path/testurl.html'");
 } catch(e) {
 debug("Exception: " + e.description);
 }
 
 debug("Set hostname to undefined");
 a.href = "https://www.mydomain.com:8080/path/";
 a.hostname = undefined;
 shouldBe("a.href", "'https://undefined:8080/path/'");