Mojo C++ bindings: introduce public associated-interface-related types.

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;
 
 interface FooInterface {};
 
 struct StructContainsAssociated {
   associated FooInterface foo_interface;
@@ skipping 10 matching lines @@
           associated FooInterface& foo_request) =>
          (associated FooInterface foo_interface,
           associated FooInterface& foo_request);
 
   PassStruct(StructContainsAssociated foo_struct) =>
             (StructContainsAssociated foo_struct);
 
   PassUnion(UnionContainsAssociated foo_union) =>
            (UnionContainsAssociated foo_union);
 };
+
+interface IntegerSender {
+  Echo(int32 value) => (int32 value);
+  Send(int32 value);
+};
+
+interface IntegerSenderConnection {
+  GetSender(associated IntegerSender& sender);
+  AsyncGetSender() => (associated IntegerSender sender);
+};