…rkRequest.

Chromium change:

https://chromium.googlesource.com/chromium/src/+/1d81619dbd351cb570943140bddac7a80559dd76

commit 1d81619dbd351cb570943140bddac7a80559dd76
Author: Clark DuVall <cduvall@chromium.org>
Date:   Fri Jul 19 19:54:42 2019 +0000

    Move WebRequest to the UI thread

    Now that network service is launched, there is no reason to have
    WebRequest run on the IO thread. This moves all WebRequest code and
    the WebRequestProxyingURLLoaderFactory to the UI thread, which
    eliminates thread hops. For more info, see the Chrome IO Thread
    Simplification: Planning doc:
    https://docs.google.com/document/d/1fowGQ8xWBv4YqHj_YbK-S3wpmJQDE7L0-GwNR_vAkHE/edit#

    Change-Id: I5ba8954c5d91c98c96a66558ecb659b59ff4386c
    Bug: 980774