GitLab

Previously chromoting host wasn't using proxies on linux because
ProxyConfigServiceLinux doesn't work in NPAPI plugins. Now it's not
a problem because we no longer support NPAPI.

BUG=410521,125104
R=jamiewalch@chromium.org, mmenke@chromium.org

Review URL: https://codereview.chromium.org/542473002

Cr-Commit-Position: refs/heads/master@{#293602}