WebKit not posting SelectedChildrenChangedNotification for combobox. Unable to use arrow keys to select items in web combo boxes. Steps To Reproduce: 1. Turn on VoiceOver > in Safari, open https://webkit.org/blog-files/aria1.0/combobox_with_live_region_status.html 2. Type "ca" in the search field, and arrow down. Results: Nothing appears to happen when pressing down arrow, VoiceOver does not speak the combo box items and does not appear to select any of the available items. Regression: The way VO handles web combo boxes has started to regress in Sierra, according to <rdar://problem/29642584> Regression: VoiceOver reads incorrect selection in web comboboxes. This appears to have further regressed since, as itβs now no longer possible to select combo box items using arrow keys at all.
Created attachment 363239 [details] testcase
<rdar://problem/44551051>