Currently in our API `?` means null, but sometimes it means optional. Linting optional/nulls with this patch is required for #1166 to land nicely.
Previously, return types were not being linted in `api.md`. This is fixed, along with many broken return types.
This patch considers `?` to mean nullable, and has some heuristics to determine optionality. I believe this to be the minimal patch needed to unblock #1166. After it lands, we can consider changing the api docs to hopefully remove some heuristics and strangeness.
This adds support for `root` in accessibility.snapshot
firefox role names are now normalized to aria roles where they match
webkit roledescriptions are less noisey on mac
webkit mac/linux results are further defined
interestingOnly tests are replaced by one that doesn't rely on undefined behavior
the main accessibility test was split up a bit for more refined testing.
