`IMEStateManager` basically runs at focus change. However, when `designMode`
is set to `"off"` or focused editing host becomes non-editable (removing
`contenteditable` attribute or `contenteditable` attribute is set to `false`),
IME may be disabled without a focus change. Therefore, `Document` needs to
notify `IMEStateManager` of the timing.
Additionally, `nsFocusManager` does not change focus when focused element
becomes not focusable (bug 1807597). Therefore, `Document` needs to kick
`focus` or `blur` event handler of `HTMLEditor` when active editing host
becomes not editable.
However, if an ancestor of focused element becomes editable, I think that
`HTMLEditor` does not work well without focus move because it computes
editing host with current editing state in a lot of places, but `Selection`
and `nsFocusManager::GetFocusedElement` keeps working with previous focused
element which is now a editable child of editing host. Therefore, this patch
marks them as `todo` in the new tests.
Differential Revision: https://phabricator.services.mozilla.com/D171196
Masayuki Nakano
Mark Banner
Brian Grinstead
Florian Quèze