Tom had the idea that we shouldn't handle file:// URLs inside the network service. We can then only send the renderer a URLLoaderFactory for the file scheme if the frame id displaying a file.
See also bug 719594 where we do this for webui. I think if we do this then this would be one less usage of CPSP that we need.
I have a CL in progress.
https://chromium-review.googlesource.com/c/chromium/src/+/1045313
Disabling file access in the network service broke some extension, download and worker tests. I fixed the extension and download cases, still need work for the worker case.
Comment 1 by bugdroid1@chromium.org
, Aug 26 2017