Also from PR #6582. An iframe is an entire browsing context, so one scrolled off
a tall board is the single most expensive thing a widget can load eagerly - and
this one had no loading attribute at all.
Records what else was mined from that PR and declined, notably its dynamic()
for BoardItemMenu: that component already early-returns null outside edit mode,
so there is no per-item overlay cost, and dynamic() fetches its chunk when the
component renders rather than when it returns something - so the chunk would
still load on every board render. It only pays off with the isEditMode guard
hoisted to the call site, which is a board-rendering change worth measuring
first rather than adopting on faith.
Thomas Camlong
839b4721fb