Make DocumentType return empty publicId by default

LayoutTests/fast/doctypes/xml-doctype.xhtml

Index: LayoutTests/fast/doctypes/xml-doctype.xhtml
diff --git a/LayoutTests/fast/doctypes/xml-doctype.xhtml b/LayoutTests/fast/doctypes/xml-doctype.xhtml
index 226735998c15d1a3131dfafe5ae0ba9b3764ab28..c589e8d7284d09666da5217cd68b20a602608d7b 100644
--- a/LayoutTests/fast/doctypes/xml-doctype.xhtml
+++ b/LayoutTests/fast/doctypes/xml-doctype.xhtml
@@ -21,6 +21,16 @@
                 log("PASS: a doctype in an XML document is correctly set to the first child of the Document.");
             else
                 log("FAIL: a doctype in an XML document is not correctly set to the first child of the Document.");
+
+            if (document.doctype.publicId == '')

[arv (Not doing code reviews), 2014/02/21 15:06:51]

Ad-hoc tests :'(

+                log("PASS: doctype.publicId correctly defaults to empty string when not set.");
+            else
+                log("FAIL: doctype.publicId does not default to empty string when not set, instead is : " + document.doctype.publicId);
+
+            if (document.doctype.systemId == '')
+                log("PASS: doctype.systemId correctly defaults to empty string when not set.");
+            else
+                log("FAIL: doctype.systemId does not default to empty string when not set, instead is : " + document.doctype.systemId);
         }
     </script>
 </head>