The only ways this varies from the `scale()` function is with parsing
and serialization. Parsing stays separate, and serialization is done by
telling `TransformationStyleValue` which property it is, and overriding
its normal `to_string()` code for properties other than `transform`.
This reverts commit 76daba3069.
We're going to need separate types for the JS-exposed style values, so
it doesn't make sense for us to match their names with our internal
types.
