Backport #43308: Only allow "about:" pages to have access to contentaccessible branding asset

Backport Patchset

Book-keeping

Gitlab Issue(s)

Merge Request(s)

Target Channels

  • Stable
  • Legacy

Notes

See !1333 (comment 3149424) for the discussion regarding backporting the two commits in !1333 (merged).

I'll leave the decision to others, since I'm finding it hard to judge the risk-benefit myself.

But it should probably at least be verified in nightly or alpha first.

  • Verified in nightly.
  • Verified in alpha.

NOTE: I set this issue to confidential since the original issue is #43308 (closed).

/cc @ma1 @pierov @morgan

Edited by morgan