Get mojo_shell building inside chromium checkout.

mojo/services/test_service/test_service.mojom

+// Copyright 2014 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 TestService {
+  Ping() => ();
+  // Connect to a TestTimeService at |app_url| and ferry the data back
+  // in |response|.
+  ConnectToAppAndGetTime(string? app_url) => (int64 time_usec);
+  StartTrackingRequests() => ();
+};
+
+interface TestTimeService {
+  // Provides a constant time value.
+  GetPartyTime() => (int64 time_usec);
+  StartTrackingRequests() => ();
+};