1367186 - Add an internal mechanism to know when visited styles are applied

Status: NEW

(Core :: CSS Parsing and Computation, enhancement, P3)

Description

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

In various tests for :visited styles, we currently use fragile things like `setTimeout` or waiting in a loop in hopes that a link is eventually visited and the visited style is applied.

We should add some kind of internal event or observer notification that can be used to know that visited styles are applied to improve the stability of these tests.

Comment 1

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

I should attempt to reland the extra visited reftests from bug 1328509 once this mechanism exists.

Comment 2

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

:emilio has another test that would be great to support in https://reviewboard.mozilla.org/r/147588/diff/1#index_header.

Comment 3

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

There's the risk that the mechanism for the notification creates a timing attack, though.

I'm curious why there were tests that didn't land.  Were they following the rules in https://searchfox.org/mozilla-central/source/layout/style/test/test_visited_reftests.html#19-24 ?