Currently when ENABLE_MOJO_MEDIA_IN_UTILITY_PROCESS is true, we register MediaService to be running in utility process at [1]. But we did not register to run the MediaService in UtilityServiceFactory. So this path is kinda broken.

Part of the reason is that this path is not used in production. So we won't have a legit MojoMediaClient impl to use except for a test one. We probably should fix it or clean it up somehow.

[1] https://www.google.com/url?q=https://cs.chromium.org/chromium/src/content/browser/service_manager/service_manager_context.cc?rcl%3D3493a0df4536fb42b5273318db56e9fece2bc0fc%26l%3D660&sa=D&source=hangouts&ust=1533770327569000&usg=AFQjCNFqF8mboA9J1kU0UKuGhkIp_TGrVQ