Lack of normative testable steps #29

For this spec to be web compatible, I think it will need normative teeth, as well as be explicit about when and where it applies. E.g. #28. In general, I think it needs to either:

1. Require other specs to normatively reference contentHint in explicit algorithms, or
2. Take it upon itself to own and specify the relevant normative language additions on behalf of the specs it wants to influence, as a form of extension spec.

Then add tests that prove functionality (beyond the current getter/setter tests).