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.
When serializing an sRGB color value that originated from a named color,
it should return the color name converted to ASCII lowercase. This
requires storing the color name (if it has one).
This change also requires explicitly removing the color names when
computing style, because computed color values do not retain their name.
It also requires removing a caching optimization in create_from_color(),
because adding the name means that the cached value might be wrong.
This fixes some WPT subtests, and also required updating some of our own
tests.
If a rule gets its caches cleared because it's moved in the OM, then its
child rules' caches are likely invalid and need clearing too.
Assuming that caches only point "upwards", this will correctly clear
them all. For the time being that will be true.
