6136444a48
Add `PlatformViewRoleManager`, the primary role manager for platform views. Currently, all it does is manager the `aria-owns` attribute that determines the screen reader traversal order of the platform view w.r.t. surrounding content. This is a partial fix for https://github.com/flutter/flutter/issues/124765. While it does not address literally using the TAB key as a means for traversing widgets, it does address traversal via screen reader shortcuts.