Add mojo struct traits for GURL so that it can be sent over mojoms.

url/mojo/url_test.mojom

Index: url/mojo/url_test.mojom
diff --git a/mash/init/public/interfaces/login.mojom b/url/mojo/url_test.mojom
similarity index 58%
copy from mash/init/public/interfaces/login.mojom
copy to url/mojo/url_test.mojom
index 3ea6f10c703ec75106ae469d3ed3ce65d53d89d0..4e1b96a1c96520922d1ed54fd8e9a05c7bfb8ab5 100644
--- a/mash/init/public/interfaces/login.mojom
+++ b/url/mojo/url_test.mojom
@@ -1,10 +1,12 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-module mash.init.mojom;
-
-interface Login {
-  LoginAs(uint32 user_id);
-};
-
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module url.mojom;
+
+import "url/mojo/url.mojom";
+
+interface UrlTest {
+  [Sync]
+  Bounce(Url in) => (Url out);
+};