DocumentOrShadowRoot APIs are marked as too new

[saschanaz]

Nearly everything there is marked as added in Chrome 53/Firefox 63, but those versions are really the ones that added ShadowRoot support. Many APIs there had been existed in Document before DocumentOrShadowRoot so we have to properly represent them.

[foolip]

Related: #472

[queengooborg]

I believe that we can resolve this by turning both Chrome and Firefox into arrays of compatibility statements. Specifically, one with the version that was added, with a partial implementation flag and a note stating "Only available in the Document API."

[foolip]

We could do that, but that wouldn't be machine readable. I think spitting the entries would be better.

@Elchi3 FYI, here's a concrete case of mixin troubles.