Activates a screen reader user and fulfill requests for accessibility services such as text to speech that clients can make. When screen reader users are first registered with a screen reader, they are deactivated by default. Users must explicitly activate the screen reader user. If the passed in user Id does not correspond to a registered screen reader user, nothing will happen.FScreenReaderReply::Handled()if the screen reader user is successfully activated. ElseFScreenReaderReply::Unhandled()is returned.