Three tests failed on a loaded machine because they asserted elapsed
time. Each now counts the work that the slow behavior it guards
against would repeat, with a counter compiled only into tests:
- The CSS cascade test counts selector tests, at most two per element
(testing every rule against every element tests N x N). It styles
5,000 elements, so the slow behavior fails on the count rather than
on the hang guard, which now waits 300 s.
- The stacked-glow test counts the silhouettes drawn, 30 for 30 glows
with and without the shadow cache.
- The Zstandard frames test counts the bytes looked at to find the
zero padding.
The hang guards for invalid dash patterns, text layout and script
checks of a pipe wait 300 s instead of 20 s.