changes for constructor

components/script/dom/mutationobserver.rs

@@ -30,11 +30,8 @@ impl MutationObserver {
 
   pub fn Constructor(global: &dom::bindings::js::Root<dom::window::Window>, callback: Rc<MutationCallback>) -> Result<Root<MutationObserver>, Error> {
   	let observer = MutationObserver::new(global, &callback);
-	match observer {
-		None => Err(Error::new()),
-  		Some(_) => Ok(dom::bindings::js::Root<MutationObserver::new(global, callback)>),
-	}
-    }
+    ScriptThread.set_mutation_observer(observer)
+  }
 
 }
 

components/script/script_thread.rs

@@ -574,6 +574,14 @@ impl ScriptThreadFactory for ScriptThread {
 }
 
 impl ScriptThread {
+    pub fn set_mutation_observer(observer: &MutationObserver) {
+        SCRIPT_THREAD_ROOT.with(|root| {
+            let script_thread = unsafe { &*root.get().unwrap() };
+            script_thread.mutation_observers
+                .push(*observer);
+        })
+    }
+
     pub fn mark_document_with_no_blocked_loads(doc: &Document) {
         SCRIPT_THREAD_ROOT.with(|root| {
             let script_thread = unsafe { &*root.get().unwrap() };