1254696 - give inIDOMUtils a method for finding types accepted by functions

Status: NEW

(Core :: CSS Parsing and Computation, defect)

Description

[Tom Tromey :tromey]

In bug 1250835, we realized that cssPropertySupportsType reports that
some properties do not take angles; but a function passed to the property
can accept an angle as an argument.

We'd like to be able to programmatically find this out for devtools.
We already have a whitelist in place for colors:
https://dxr.mozilla.org/mozilla-central/source/devtools/client/shared/output-parser.js#17
... and we'll probably be adding another for angles.

It would be more future-proof if this information were exposed to
devtools from platform.