AccessibleCarets are anonymous contents created by nsCanvasFrame::CreateAnonymousContent() in http://searchfox.org/mozilla-central/rev/ae8c2e2354db652950fe0ec16983360c21857f2a/layout/generic/nsCanvasFrame.cpp#117 It's available on platforms which support touch events (such as Fennec or Windows with touch screen).
I don't know which commit fixed this, but AccessibleCaret is working on stylo now. Test on my local build on this commit. https://hg.mozilla.org/mozilla-central/rev/b266a8d8fd59
Status: NEW → RESOLVED
Last Resolved: a year ago
Resolution: --- → WORKSFORME
You need to log in before you can comment on or make changes to this bug.