1833878 - Remove range workaround in parseXULToFragment

Status: NEW

(Toolkit :: UI Widgets, task)

Description

[Brian Grinstead [:bgrins]]

We have this unusual workaround at the bottom of parseXULToFragment which was added to work around how XBL worked: https://searchfox.org/mozilla-central/rev/2ca95198a2a0806de358a0484d96d4354e3cbaab/toolkit/content/customElements.js#572-576. This was used to get access to the element without touching it with JavaScript (and thus eagerly constructing XBL elements before layout).

I don't see any reason why this would still be needed, and there may be a small perf win from removing it.