Add quirk `elementBCRIgnoresBodyScroll` and it's
workaround in DomUtils.getBoundingClientRect.

When the body has scrolled, an element/range's BCR
should update to reflect the new coordinates.

Instead, in iOS Safari, an element's BCR remains the
same that happens.

This workaround attempts to trigger a quick bodyscroll
and detects this quirk by measuring the BCRs of a
test element before and after.