add readonly pathname function in location

pathname function implemented in UrlHelper
'url is null' check is skip for now

components/script/dom/location.rs

@@ -46,6 +46,10 @@ impl<'a> LocationMethods for JSRef<'a, Location> {
         UrlHelper::Href(&self.get_url())
     }
 
+    fn Pathname(self) -> USVString {
+        UrlHelper::Pathname(&self.get_url())
+    }
+
     fn Stringify(self) -> DOMString {
         self.Href().0
     }

components/script/dom/urlhelper.rs

@@ -4,7 +4,7 @@
 
 use dom::bindings::str::USVString;
 
-use url::Url;
+use url::{Url, SchemeData};
 
 use std::borrow::ToOwned;
 
@@ -31,6 +31,15 @@ impl UrlHelper {
         })
     }
 
+    pub fn Pathname(url: &Url) -> USVString {
+        // https://url.spec.whatwg.org/#dom-urlutils-pathname
+        // FIXME: Url null check is skipped for now
+        USVString(match url.scheme_data {
+            SchemeData::NonRelative(ref scheme_data) => scheme_data.clone(),
+            SchemeData::Relative(..) => url.serialize_path().unwrap()
+        })
+    }
+
     /// https://html.spec.whatwg.org/multipage/browsers.html#same-origin
     pub fn SameOrigin(urlA: &Url, urlB: &Url) -> bool {
         if urlA.host() != urlB.host() {

components/script/dom/webidls/URLUtils.webidl

@@ -16,6 +16,7 @@ interface URLUtils {
   //         attribute USVString hostname;
   //         attribute USVString port;
   //         attribute USVString pathname;
+  readonly attribute USVString pathname;
   //         attribute USVString search;
   readonly attribute USVString search;
   //         attribute URLSearchParams searchParams;