added Mutation Observer Constructor

components/script/dom/mutationobserver.rs

@@ -1,18 +1,41 @@
 use core::ptr::null;
+use dom;
 use dom_struct::dom_struct;
+use dom::bindings::codegen::Bindings::MutationObserverBinding::MutationCallback;
 use dom::bindings::codegen::Bindings::MutationObserverBinding::MutationObserverBinding::MutationObserverMethods;
 use dom::bindings::codegen::Bindings::MutationObserverBinding::MutationObserverInit;
+use dom::bindings::error::Error;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::Reflector;
+use dom::bindings::trace::JSTraceable;
 use dom::mutationrecord::MutationRecord;
 use dom::node::Node;
+use dom::window::Window;
+use std::rc::Rc;
 
 #[dom_struct]
 pub struct MutationObserver {
   reflector_: Reflector,
+  callback: MutationCallback,
 }
 
 impl MutationObserver {
+
+   fn new(global: &dom::bindings::js::Root<dom::window::Window>, callback: MutationCallback) -> MutationObserver {
+        MutationObserver {
+            reflector_: Reflector::new(),
+            callback: callback,
+        }
+    }
+
+  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)>),
+	}
+    }
+
 }
 
 impl MutationObserverMethods for MutationObserver {