Mojo: Implement support for |Foo&| mojom syntax

mojo/services/native_viewport/native_viewport.mojom

 // Copyright 2013 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.
 
+import "../gles2/command_buffer.mojom"
 import "../public/interfaces/geometry/geometry.mojom"
 import "../public/interfaces/input_events/input_events.mojom"
 
 module mojo {
 
 [Client=NativeViewportClient]
 interface NativeViewport {
   Create(Rect bounds);
   Show();
   Hide();
   Close();
   SetBounds(Rect bounds);
-  CreateGLES2Context(handle<message_pipe> gles2_client);
+  CreateGLES2Context(CommandBuffer& gles2_client);
 };
 
 interface NativeViewportClient {
   OnCreated();
   OnBoundsChanged(Rect bounds);
   OnDestroyed();
   OnEvent(Event event) => ();
 };
 
 }