WebRTC not fully disabled with Tor

[tildelowengrimm]

Test Plan

• download the latest 0.23.x build that includes Tor
• visit https://browserleaks.com/webrtc within a Tor PT
• ensure that nothing is being listed under Device Enumeration, Has Microphone, Has Camera and Media Devices
• Disable shields, ensure that nothing is being listed under Device Enumeration, Has Microphone, Has Camera and Media Devices

See an example of a failing example via the screenshot @flamsmark added into the original issue.

Original Bug

In a private tab with Tor, it doesn't look like WebRTC is fully disabled. Visiting https://browserleaks.com/webrtc with default shields settings caused Brave to access my webcam drivers and then expose a list of A/V devices to the site. IP address doesn't seem to have been exposed.

Related: #13397.

I'm using the test build with Tor available for private tabs.

Brave: 0.23.2
V8: 6.6.346.26
rev: c09cbf6
Muon: 6.1.0
OS Release: 17.5.0
Update Channel: Developer
OS Architecture: x64
OS Platform: macOS
Node.js: 7.9.0
Brave Sync: v1.4.2
libchromiumcontent: 66.0.3359.139

[riastradh-brave]

What we automatically block in private tabs with Tor enabled is only the WebRTC IP leak. We do not automatically block all (first-party) fingerprinting, but if you enable that in shields, then (some?) WebRTC fingerprinting methods are blocked. (Third-party fingerprinting is blocked by default.)

[diracdeltas]

if we turned on #13735, it would also block device enumerator in tor tabs

[diracdeltas]

i think this is actually fixed with #14402

[jumde]

Fixed by: #14402
Commit: 051109c

[srirambv]

Verified on Windows 10 x64 using

• 0.23.16 - 2042c45
• Muon - 7.1.1
• libchromiumcontent - 67.0.3396.87

Verified with macOS 10.12.6 using

• 0.23.17 bc754eb
• Muon 7.1.2
• libchromiumcontent 67.0.3396.87

Verified on Ubuntu 18.04 x64 using the following build:

• 0.23.17 bc754eb
• muon: 7.1.2
• libchromiumcontent: 67.0.3396.87