dispatch toggleevents for dialog open/close

[keithamus]

WebKittens

@annevk @rniwa @nt1m

Title of the proposal

Dispatch beforetoggle & toggle events during dialog open/close/showModal

URL to the spec

whatwg/html#10091

URL to the spec's repository

https://github.com/whatwg/html

Issue Tracker URL

No response

Explainer URL

No response

TAG Design Review URL

No response

Mozilla standards-positions issue URL

mozilla/standards-positions#1101

WebKit Bugzilla URL

No response

Radar URL

No response

Description

Gecko is shipping this in nightly, Chrome is shipping flagged, but I will be submitting an I2S very shortly.

[nt1m]

I'll mark this as supportive in a week pending objections.