Different users of BooleanExpression have different requirements for
evaluation:
- `@media` needs a Document
- `@supports` doesn't need anything
- `@container` needs a container Element
To support these without expanding the API, replace the Document*
parameter with a BooleanExpressionEvaluationContext type which contains
these different values.
No behaviour changes.
Previously we would always use the window's viewport which was incorrect
if we were within an iframe.
This is likely applicable to all uses of
`Length::ResolutionContext::for_window`.
CSS Values 5 now defines a `<boolean-expr[]>` type that is used in place
of the bespoke grammar that previously existed for `@media` and
`@supports` queries. This commit implements some BooleanExpression
types to represent the nodes in a `<boolean-expr[]>`, and reimplements
`@media` and `@supports` queries using this.
The one part of this implementation I'm not convinced on is that the
`evaluate()` methods take a `HTML::Window*`. This is a compromise
because `@media` requires a Window, and `@supports` does not require
anything at all. As more users of `<boolean-expr[]>` get implemented in
the future, it will become clear if this is sufficient, or if we need
to do something smarter.
As a bonus, this actually improves our serialization of media queries!
