Add comment explaining why chrome_proxy.exe exists

Bug: 732357
Change-Id: Iedae967997bade3143ba6a2b8bd8e5fb43534ca2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1585399
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Bugs Nash <bugsnash@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654322}
1 file changed