The test reads window.outerWidth and screen.* from the content process right
after setViewportSize resolves. In an RDM pane those values come from the last
dimensions the parent sent the content process, and the parent only sends them
from its refresh driver tick, in nsRefreshDriver::Tick ->
UpdateRemoteFrameEffects. setViewportSize resolves before that happens, so the
test can measure the pre-RDM size.
On this configuration the test loses that race consistently, which blocks the
WR_FEATURE_SUPERELLIPSE shader patches from landing. Disable it there while the
test fix is reviewed separately.
browser_viewport_changed_meta.js and browser_viewport_zoom_resolution_invariant.js
are already disabled on the same configuration for related races.
Differential Revision: https://phabricator.services.mozilla.com/D320211
Nicolas Silva
f7f450757e