Upgrade Sky's use of the JS bindings

sky/framework/xmlhttprequest.sky

Index: sky/framework/xmlhttprequest.sky
diff --git a/sky/framework/xmlhttprequest.sky b/sky/framework/xmlhttprequest.sky
index ef132650cada24ed1f44aac58a35d9ec30c84f2e..7df72b17532d6681a50e1d1f266688921c33a6d2 100644
--- a/sky/framework/xmlhttprequest.sky
+++ b/sky/framework/xmlhttprequest.sky
@@ -101,10 +101,9 @@ class XMLHttpRequest {
     });
     priv.request.headers = requestHeaders;
 
-    // FIXME: Factor this into the JS bindings.
-    var pipe = new core.createMessagePipe();
-    priv.networkService.createURLLoader(pipe.handle1);
-    priv.loader = shell.wrapHandle(pipe.handle0, loader.URLLoader);
+    priv.networkService.createURLLoader(function(urlLoaderProxy) {
+        priv.loader = urlLoaderProxy;
+    });
 
     var self = this;
     outstandingRequests.add(this);