Set apz.scrollend-event.content.enabled=true to fire scrollend events to content by default, and let the feature ride the trains.

Enable firing the scrollend event to content by default.

Backed out for causing wpt failures on math-global-event-handlers.tentative.html

• Backout link
• Push with failures
• Failure Log
• Failure line: TEST-UNEXPECTED-PASS | /mathml/relations/html5-tree/math-global-event-handlers.tentative.html | onscrollend: must be on the appropriate locations for GlobalEventHandlers - expected FAIL

(In reply to Cristian Tuns from comment #3)

Backed out for causing wpt failures on math-global-event-handlers.tentative.html

• Backout link
• Push with failures
• Failure Log
• Failure line: TEST-UNEXPECTED-PASS | /mathml/relations/html5-tree/math-global-event-handlers.tentative.html | onscrollend: must be on the appropriate locations for GlobalEventHandlers - expected FAIL

Looks like new wpt tests that should pass with apz.scrollend-event.content.enabled=true. Updated the test expectations.

https://hg.mozilla.org/mozilla-central/rev/848de6ab7ca9

We're tracking documentation changes for this in the following GitHub issue -> https://github.com/mdn/content/issues/22814

Release Note Request (optional, but appreciated)
[Why is this notable]: Adds a new event scrollend which is fired when a scroll has completed.
[Affects Firefox for Android]:
[Suggested wording]: scrollend events fired to content by default on scroll completed.
[Links (documentation, blog post, etc)]:

• MDN Document: scrollend
• MDN Element: scrollend