fn parse_font_face_descriptors(
global: &GlobalScope,
family_name: &DOMString,
sources: Option<&DOMString>,
input_descriptors: &FontFaceDescriptors,
) -> Fallible<FontFaceRule>Expand description
Given the various font face descriptors, construct the equivalent @font-face css rule as a
string and parse it using style crate. Returns Err(Error::Syntax) if parsing fails.
Due to lack of support in the style crate, parsing the whole @font-face rule is much easier
to implement than parsing each declaration on its own.