Rename files relating to PAC (proxy auto config).

This renames files starting with proxy_script_* and proxy_resolver_script* to start with pac_file*.  It does not rename any of the actual classes (e.g., DhcpProxyScriptFetcher), which will need to be done in a followup CL.

NOPRESUBMIT=true
TBR=yhirano@chromium.org,mmenke@chromium.org

Bug: 613655
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I35888c47b67ef886ea459f1c11ca5a66df22a097
Reviewed-on: https://chromium-review.googlesource.com/836927
Commit-Queue: Lily Houghton <lilyhoughton@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#530758}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 9844d32d14c734507965962bdd5c499ac4b657fc
2 files changed