r520479 is causing flaky failures in interactive_ui_tests on debug Windows configurations (see issue 790935):

[19476:18816:1201/162752.848:FATAL:web_service_worker_registration_impl.cc(225)] Check failed: LifecycleState::kDetached == state_ (2 vs. 1)
Backtrace:
...
        content::WebServiceWorkerRegistrationImpl::OnConnectionError [0x11600E89+457]
...
        mojo::InterfaceEndpointClient::NotifyError [0x10B44C1F+351]
        scoped_refptr<base::SequencedTaskRunner>::scoped_refptr<base::SequencedTaskRunner> [0x10CCD893+483]
        base::Optional<mojo::DisconnectReason>::Optional<mojo::DisconnectReason> [0x10CCDF0A+810]
...

I will attempt a revert.