Add an end-to-end test that excercises Mojo with a sandbox.

content/content_common_mojo_bindings.gyp

 # 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.
 
 {
   'targets': [
     {
       # GN version: //content/common:mojo_bindings
       'target_name': 'content_common_mojo_bindings_mojom',
       'type': 'none',
       'variables': {
         'mojom_extra_generator_args': [
           '--typemap', '<(DEPTH)/url/mojo/origin.typemap',
         ],
         'mojom_files': [
           # NOTE: Sources duplicated in //content/common/BUILD.gn:mojo_bindings.
           'common/application_setup.mojom',
           'common/background_sync_service.mojom',
           'common/geolocation_service.mojom',
           'common/image_downloader/image_downloader.mojom',
           'common/leveldb_wrapper.mojom',
+          'common/mojo_test.mojom',
           'common/permission_service.mojom',
           'common/presentation/presentation_service.mojom',
           'common/process_control.mojom',
           'common/render_frame_setup.mojom',
           'common/service_port_service.mojom',
           'common/service_worker/embedded_worker_setup.mojom',
           'common/storage_partition_service.mojom',
           'common/vr_service.mojom',
           'common/wake_lock_service.mojom',
 
@@ skipping 24 matching lines @@
       'type': 'static_library',
       'variables': {
         'enable_wexit_time_destructors': 1,
       },
       'dependencies': [
         'content_common_mojo_bindings_mojom',
       ],
     },
   ]
 }