Switch URL and URLUtils interfaces over to use ScalarValueString.

LayoutTests/fast/domurl/url-host.html

Index: LayoutTests/fast/domurl/url-host.html
diff --git a/LayoutTests/fast/domurl/url-host.html b/LayoutTests/fast/domurl/url-host.html
index fe68d4f62b807ab7d1e1c93bf5cebc0bd205f960..1193969b6513e0c0c0bedffcfd5f0c64de5f344f 100644
--- a/LayoutTests/fast/domurl/url-host.html
+++ b/LayoutTests/fast/domurl/url-host.html
@@ -107,4 +107,12 @@ test(function() {
     assert_equals(url.href, 'invalid');
 }, 'host property invalid URL');
 
+test(function() {
+    var url = new URL('http://www.domain.com/');
+    assert_equals(url.host, 'www.domain.com');
+
+    url.host = 'www.bo\udc01\ud802gus.org';
+    assert_equals(url.host, '');
+}, 'hostname with unmatched surrogates');
+
 </script>