i've seen this recently on all 3 platforms, using comm branch bits [haven't played with trunk bits that much recently]. most often see it when using the modern theme, but sometimes i see it with classic as well. essentially, the first time a dialog with a checkbox appears, i cannot see the checkmark. most often see this with the download/helper app dialog, but i've seen this with the mail password dialog [when the password manager/single signon is enabled]. subsequent attempts in the same session will not display this problem.
very annoying regression. it reminds me of bug 80600 --except there it was the text for checkboxes not showing up.
works for me - I've never even seen this.