Expose Brave UA String via navigator.userAgent on select origins

[jonathansampson]

Description

Brave currently exposes a custom user agent string in the HTTP request headers for select domains. This does not, however, change the value stored in navigator.userAgent for those same origins.

https://github.com/brave/brave-core/blob/66ceaf3491778f7d9a62f215c8fb47b318c9b181/browser/net/brave_site_hacks_network_delegate_helper.cc#L66-L74

Steps to Reproduce

Go to a whitelisted domain (e.g. duckduckgo.com) and log navigator.userAgent in the console.

Actual result:

Brave token not present.

Expected result:

Brave token should be present, as it is in the request header for the document.

Reproduces how often:

Always.

Brave version (brave://version info)

0.69.132

Other Additional Information:

I believe the requested behavior was present in earlier Muon builds.

[bsclifton]

Closing in favor of #8216

• solution in Desktop :: Implement "Enabling Sites to Determine Brave" Spec #8216 will allow detection of Brave
• Chromium is looking at Freezing the UA. More info available:
  • https://www.chromestatus.com/feature/5704553745874944
  • https://bugs.chromium.org/p/chromium/issues/detail?id=955620
• no inclusion/exclusion list needed
• not modifying UA lowers web compatibility risks