The native key message in the form of a raw key event.
A native key message is sent to the framework in JSON and represented in a platform-specific form as RawKeyEventData and a platform-neutral form as RawKeyEvent. Their stream is not as regular as KeyEvent's, but keeps as much native information and structure as possible.
The rawEvent field might be empty, for example, when the event converting system dispatches solitary synthesized events.
The rawEvent field will be deprecated in the future.
final RawKeyEvent? rawEvent;