Mojo: Add a trivial end-to-end (in-process) test of Mojo shell.

mojo/mojo_services.gypi

 {
   'targets': [
     {
       'target_name': 'mojo_echo_bindings',
       'type': 'static_library',
       'sources': [
         'services/dbus_echo/echo.mojom',
       ],
       'includes': [ 'public/tools/bindings/mojom_bindings_generator.gypi' ],
       'export_dependent_settings': [
@@ skipping 299 matching lines @@
           'dependencies': [
             'mojo_view_manager_run_unittests'
           ],
         }, {  # use_aura==0
           'dependencies': [
             'mojo_run_all_unittests',
           ],
         }]
       ],
     },
+    {
+      'target_name': 'mojo_test_service_bindings',
+      'type': 'static_library',
+      'sources': [
+        'services/test_service/test_service.mojom',
+      ],
+      'includes': [ 'public/tools/bindings/mojom_bindings_generator.gypi' ],
+      'export_dependent_settings': [
+        'mojo_cpp_bindings',
+      ],
+      'dependencies': [
+        'mojo_cpp_bindings',
+      ],
+    },
+    {
+      'target_name': 'mojo_test_service',
+      'type': 'shared_library',
+      'dependencies': [
+        '../base/base.gyp:base',
+        'mojo_application',
+        'mojo_common_lib',
+        'mojo_environment_standalone',
+        'mojo_test_service_bindings',
+        'mojo_system_impl',
+        'mojo_utility',
+      ],
+      'sources': [
+        'public/cpp/application/lib/mojo_main_standalone.cc',
+        'services/test_service/application.cc',
+        'services/test_service/test_service_impl.cc',
+        'services/test_service/test_service_impl.h',
+      ],
+    },
   ],
   'conditions': [
     ['use_aura==1', {
       'targets': [
         {
           'target_name': 'mojo_view_manager',
           'type': '<(component)',
           'dependencies': [
             '../base/base.gyp:base',
             '../skia/skia.gyp:skia',
@@ skipping 109 matching lines @@
             'mojo_system_impl',
           ],
           'sources': [
             'services/dbus_echo/dbus_echo_service.cc',
           ],
         },
       ],
     }],
   ],
 }