Fifo order should be preserved for messages on associated interfaces.

mojo/public/interfaces/bindings/tests/test_associated_interfaces.mojom

 // Copyright 2015 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 mojo.test;
 
 import "mojo/public/interfaces/bindings/tests/ping_service.mojom";
 
 interface FooInterface {};
 
@@ skipping 22 matching lines @@
 
   PassUnion(UnionContainsAssociated foo_union) =>
            (UnionContainsAssociated foo_union);
 };
 
 interface IntegerSender {
   Echo(int32 value) => (int32 value);
   Send(int32 value);
 };
 
+interface StringSender {
+  Echo(string value) => (string value);
+  Send(string value);
+};
+
 interface IntegerSenderConnection {
   GetSender(associated IntegerSender& sender);
   AsyncGetSender() => (associated IntegerSender sender);
 };
 
 interface IntegerSenderConnectionAtBothEnds {
   GetSender(associated IntegerSender& sender);
   SetSender(associated IntegerSender sender) => (int32 value);
 };
 
+interface SenderConnection {
+  GetIntegerSender(associated IntegerSender& sender);
+  GetStringSender(associated StringSender& sender);
+};
+
 interface AssociatedPingProvider {
   GetPing(associated PingService& request);
 };
 
 interface AssociatedPingProviderProvider {
   GetPingProvider(associated AssociatedPingProvider& request);
 };