Proxy Automatic Configuration on MacOS does not work

[loklaan]

Description

Brave does not respect system settings for Automatic Proxy Configuration.

Steps to Reproduce

1. Setup a local Proxy Automatic Configuration (.pac)
   I stumbled on this issue while attempting to setup hotel, which may be a useful starting point.
2. Paste the URL to a .pac file in: Networking > Advanced... > Proxies > Automatic Proxy Configuration > URL
3. Restart your network & brave, as recommended.
4. Navigate to a URL you expect to be proxied. It won't work as expected.
   When using hotel, I expected hotel.localhost to be proxied.

Actual result:

I was taken to the ERR_CONNECTION_REFUSED error screen.

eg. "hotel.localhost refused to connect."

Expected result:

It should have connected to the proxied URL.

hotel.localhost > localhost:2000

Reproduces how often:

Constant.

Brave version (brave://version info)

Info:

Item	Description
Brave	0.66.101 Chromium: 75.0.3770.142 (Official Build) (64-bit)
Revision	8d93477bd18154c67a70a67019cb8032382c55dd-refs/branch-heads/3770@{#1160}
OS	Mac OS X

Version/Channel Information:

• Can you reproduce this issue with the current release?
  Yes
• Can you reproduce this issue with the beta channel?
  Have not tried. The beta changelog didn't mention any fix.
• Can you reproduce this issue with the dev channel?
  Have not tried. The dev changelog didn't mention any fix.
• Can you reproduce this issue with the nightly channel?
  Have not tried. The commitlog didn't mention any fix.

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
  No
• Does the issue resolve itself when disabling Brave Rewards?
  No
• Is the issue reproducible on the latest version of Chrome?
  No (it works fine)

Miscellaneous Information:

As mentioned, it may be good to reproduce my exact path-to-error by attempting to setup local url proxying for https://github.com/typicode/hotel/, on MacOS.