validity.valueMissing should not rely on element's disabled state for inputs of type radio/file/checkbox.
Created attachment 445633 [details] Patch
Created attachment 445665 [details] Patch
Committed r286413 (244759@main): <https://commits.webkit.org/244759@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 445665 [details].
<rdar://problem/85955382>