GitLab

Introduce the fake network context class, used by unit tests, to avoid
duplication across multiple routines.

BUG=chromium:956783
TEST=none

Change-Id: I536a208c32a6454c832847325eb3d933d357b40c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434092Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Kartik Hegde <khegde@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812443}