We don't support all parts of the font formats we assume as "supported"
in the CSS parser. For example, if an open type font has a CFF table, we
reject loading it. This meant that until now, when such an
unsupported-supported font url was first in the list of urls, we
couldn't load it at all, even when we would support a later url.
To resolve that, try loading all font urls one after each other, in case
we are not able to load the higher priority one.
This also resolves a FIXME related to spec compliant url prioritization.
Our CSS parser already filters and prioritizes font src urls in
compliance with the spec. However, we still had to resort to brittle
file extension matching, because some websites don't set the `format`
and if the first url in a src list happened to be one we don't support,
the font could not be loaded at all. This now is unnecessary because we
can try and discard the urls instead.
Use FlyString::from_deprecated_fly_string() in these instances instead
of FlyString::from_utf8(). As we convert to new FlyString/String we want
to be aware of these potential unnecessary allocations.
This relied on pulling the current realm from the main thread VM, which
requires an execution context to be on the VM's stack. This heavily
relied on the dummy execution context that is always on the stack, for
example, when parsing the UA style sheets where no JavaScript is
running.
This requires Parser to be movable, so we remove the `default`
destructors from Parser and TokenStream, and give them both move
constructors. Since TokenStream only holds a reference to its tokens,
(and it needs to, to avoid copying when given eg a function's contents,)
we add a manual move constructor for Parser which creates a new
TokenStream from the new Parser's tokens, and then manually copies the
old TokenStream's state.
Instead of constructing a Tokenizer and then calling parse() on it, we
now call `Tokenizer::tokenize(...)` directly. (Renamed from `parse()`
because this is a Tokenizer, not a Parser.)
