ChromeNetworkDelegate has been removed and we can't subclass it any
more. It is also no longer needed when network service is used.

Chromium change:

https://chromium.googlesource.com/chromium/src/+/3576e9bf0861248a7b3e7133b9e4c216f0e19819

commit 3576e9bf0861248a7b3e7133b9e4c216f0e19819
Author: John Abd-El-Malek <jam@chromium.org>
Date:   Thu Jun 6 22:25:50 2019 +0000

    Remove ChromeNetworkDelegate.

    The implementation is gone, but I've left the files because the IsAccessAllowed methods which aren't specific to the NetworkDelegate aspect of this are still used. I'll rename them in a followup.

    Bug: 934009