auto merge of #5457 : deokjinkim/servo/navigator_appversion, r=jdm

In my mistake, I close PR for this commit.
I'm sorry for inconvenience.

@jdm 's comment
The test expectations for /tests/wpt/web-platform-tests/html/dom/interfaces.html and /tests/wpt/web-platform-tests/workers/interfaces.workers.js will need to be updated - http://mxr.mozilla.org/servo/search?string=appversion

According to your guide, I revised commit. Is this your intention?
r? @jdm 

cc @yichoi

components/script/dom/navigator.rs

@@ -54,5 +54,9 @@ impl<'a> NavigatorMethods for JSRef<'a, Navigator> {
     fn UserAgent(self) -> DOMString {
         navigatorinfo::UserAgent()
     }
+
+    fn AppVersion(self) -> DOMString {
+        navigatorinfo::AppVersion()
+    }
 }
 

components/script/dom/navigatorinfo.rs

@@ -33,3 +33,7 @@ pub fn UserAgent() -> DOMString {
         None => "".to_owned(),
     }
 }
+
+pub fn AppVersion() -> DOMString {
+    "4.0".to_owned()
+}

components/script/dom/webidls/Navigator.webidl

@@ -19,7 +19,7 @@ Navigator implements NavigatorID;
 interface NavigatorID {
   readonly attribute DOMString appCodeName; // constant "Mozilla"
   readonly attribute DOMString appName;
-  //readonly attribute DOMString appVersion;
+  readonly attribute DOMString appVersion;
   readonly attribute DOMString platform;
   readonly attribute DOMString product; // constant "Gecko"
   boolean taintEnabled(); // constant false

components/script/dom/workernavigator.rs

@@ -55,5 +55,9 @@ impl<'a> WorkerNavigatorMethods for JSRef<'a, WorkerNavigator> {
     fn UserAgent(self) -> DOMString {
         navigatorinfo::UserAgent()
     }
+
+    fn AppVersion(self) -> DOMString {
+        navigatorinfo::AppVersion()
+    }
 }