Mojo: Pass URLLoader to ResponseDetails as interface rather than handle.

mojo/services/public/interfaces/navigation/navigation.mojom

Index: mojo/services/public/interfaces/navigation/navigation.mojom
diff --git a/mojo/services/public/interfaces/navigation/navigation.mojom b/mojo/services/public/interfaces/navigation/navigation.mojom
index 5254bf041904c7a7b9bbb2105d8d5e551e6a0540..fd51d0647e5d4b5c86ea155bfa802c54ab39601c 100644
--- a/mojo/services/public/interfaces/navigation/navigation.mojom
+++ b/mojo/services/public/interfaces/navigation/navigation.mojom
@@ -27,12 +27,11 @@ struct ResponseDetails {
   // TODO(beng): consider providing access to URLRequest too. Currently it is
   //             not possible to obtain from the URLLoader.
 
+  mojo.URLResponse response;
+
   // The URLLoader instance that generated the response. This must be kept
   // alive until the response body has been completely consumed.
-  // TODO(darin): This should be |mojo.URLLoader loader|. See crbug/392693.
-  handle<message_pipe> loader_handle;
-
-  mojo.URLResponse response;
+  mojo.URLLoader loader;
 };
 
 // Embedders that support navigation of implement this interface.