Review request for RT-19228

[Richard Bair]

> So a builder might be a good way to address this particular issue. However, I don't think that using a builder here necessarily invalidates the fx:constant concept. FXML currently lacks a standard way to refer to constants, and I think fx:constant would be a nice, consistent way to do it.

I agree, in the issue report I listed 4 potential approaches that all seemed reasonable and not mutually exclusive, and this is one of the solutions.