Function parse_css_declaration 

pub fn parse_css_declaration<'a>(
    unparsed_css_key: &'a str,
    unparsed_css_value: &'a str,
    location: ErrorLocationRange,
    css_key_map: &CssKeyMap,
    warnings: &mut Vec<CssParseWarnMsg<'a>>,
    declarations: &mut Vec<CssDeclaration>,
) -> Result<(), CssParseErrorInner<'a>>

Parses a single CSS key-value declaration, appending results to declarations.

Unknown property keys are downgraded to warnings (pushed into warnings) rather than causing a hard error, so callers can continue processing the remaining declarations in a rule block.