This function was removed along with url_request_mock_util.h.

Chromium change:

https://chromium.googlesource.com/chromium/src/+/779c64cbc9bf21539fe7b712df43b79952086704

commit 779c64cbc9bf21539fe7b712df43b79952086704
Author: Clark DuVall <cduvall@chromium.org>
Date:   Wed Jun 12 22:31:58 2019 +0000

    Cleanup unnecessary non-network service code

    Bug: 934009