Scrollable overflow still assumed a top-left scroll origin and only
added trailing padding on the physical bottom edge. That broke
scrollWidth and scrollHeight for flex containers whose main or cross
axis was reversed by writing-mode, direction, flex-direction, or
wrap-reverse.
Teach flex layout to place wrapped lines using the computed cross-axis
direction and to measure scrollable overflow from the container's
actual scroll origin so reachable reversed overflow is preserved, the
unreachable side is clipped, and end padding is added on the correct
physical edge.
Keep per-item cross-axis placement using the existing behavior.
Applying full cross-axis reversal there regressed baseline alignment
tests, and zero-sized boxes exactly at the scroll origin must still
contribute descendant overflow, so the unreachable-overflow checks
need strict comparisons.
This makes negative-overflow-002 and negative-overflow-003 pass and
improves negative-overflow, align-content-wrap-003, and
overflow-with-padding.
Whenever we end up with a scrollable overflow rect that goes beyond
either of its axes (i.e. the rect has a negative X or Y position
relative to its parent's absolute padding box position), we need to clip
that rect to prevent going into the "unreachable scrollable overflow".
This fixes the horizontal scrolling on https://ladybird.org (gets more
pronounced if you make the window very narrow).
This allows us to disable test output, which performs expensive assert
tracking. This was making our imported tests run significantly slower
than tests run via `WPT.sh`.
Formatting the output ourselves also allows us to remove unnecessary
information from the test output.
This commit also rebaselines all existing imported WPT tests to follow
the new format.
In particular, this property now interacts correctly when the flex
container has flex-wrap: wrap-reverse.
This caused some "regressions" in WPT tests for negative overflow in
flex containers, but the previous behavior wasn't correct either,
it just happened to give false positives on tests.
