requestFocus abstract method
Queue-and-retry counterpart of setFocus, for a focus action.
A focus action runs while the state machine advances, before the update pass has refreshed whether the target is focusable, so applying it there can reject a target that is perfectly focusable by the time the frame is drawn. Queue instead; processAllPendingFocusRequests applies it.
Implementation
void requestFocus(FocusNode node);