To prepare for introducing a CSS::URL type, we need to qualify any use
of LibURL as `::URL::foo` instead of `URL::foo` so the compiler doesn't
get confused.
Many of these uses will be replaced, but I don't want to mix this in
with what will likely already be a large change.
Read the descriptor style values instead of producing a ParsedFontFace
first, as this means we know if a descriptor is actually present, or
has been defaulted to an initial value. This lets us correctly skip the
unicode-range if it was not explicitly set.
Firefox and Chromium both serialize using the "font-stretch" name,
(which is an alias for font-width) which follows the outdated cssom
spec, so I've done so too to match them.
The one thing that we still do differently in this test is that those
browsers check explicitly if `font-stretch` was set, and ignore when
`font-width` is.
I've also inlined the `serialize_a_local()` function to the one place
it's used. The style value to_string() method was already wrapping the
string in quotes, so calling serialize_a_string() on it was producing
`local("\this mess\"")`. It's clearer what's happening when the code
isn't split up.
