[Desktop] Incorrect UserAgent is causing Unsupported OS error on some sites

[jumde]

Description

Unknown in UserAgent is causing issues on sites like zoom

Steps to Reproduce

1. Navigate to Devtools > Console
2. Execute navigator.userAgent

Actual result:

navigator.userAgent
"Mozilla/5.0 (Unknown; Intel Mac OS X ) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.30 Safari/537.36"

Expected result:

navigator.userAgent
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.102 Safari/537.36"

Reproduces how often:

Easily

Brave version (brave://version info)

1.16.14 Chromium: 86.0.4240.30 (Official Build) nightly (x86_64)

Version/Channel Information:

• Can you reproduce this issue with the current release? No
• Can you reproduce this issue with the beta channel? No
• Can you reproduce this issue with the nightly channel? Yes

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

[kjozwiak]

Verification PASSED on macOS 10.15.6 x64 using the following build:

Brave | 1.16.17 Chromium: 86.0.4240.30 (Official Build) nightly (x86_64)
-- | --
Revision | 09f50eb5535879364cf00e72653462a509ef6bdc-refs/branch-heads/4240@{#552}
OS | macOS Version 10.15.6 (Build 19G73)

Went through the STR/Cases outlined via #11707 (comment) and ensured the correct user agent was being used as per the following:

--> navigator.userAgent

"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.30 Safari/537.36"

Also checked http://google.ca/ by searching what is my user agent and ensured the correct UA was being displayed: