769207 - (removemutationevents) Get rid of mutation events

Status: NEW

(Core :: DOM: Events, task, P3)

Description

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Mutation events are synchronous, which causes a ludicrous number of bugs and performance issues.  We now have mutation observers, and we'd really like to kill support for mutation events at some point in the future.  Probably not for a while yet.

In bug 766426 I'm going to have to add some kind of hack to account for mutation events, maybe removing an assert.  So I'd like to file a followup to get rid of the hack once we get rid of mutation events, and have it depend on this so we hopefully remember to fix it when we do actually kill mutation events.

Comment 1

[Simon Pieters [:zcorpan]]

Per https://github.com/whatwg/dom/issues/305#issuecomment-2302407051 the rollout of removed mutation events is now 99% of Chrome users, though there's an origin trial to keep mutation events supported.

I think we can turn off mutation events in Nightly and also offer an origin trial to keep them supported. When the number of sites in Chrome's origin trial is very low or they remove the origin trial, we should be able to ship to release.