Whether this event is synthesized by Flutter to synchronize key states.
An non-synthesized event is converted from a native event, and a native event can only be converted to one non-synthesized event. Some properties might be changed during the conversion (for example, a native repeat event might be converted to a Flutter down event when necessary.)
A synthesized event is created without a source native event in order to synchronize key states. For example, if the native platform shows that a shift key that was previously held has been released somehow without the key up event dispatched (probably due to loss of focus), a synthesized key up event will be added to regularized the event stream.
For detailed introduction to the regularized event model, see HardwareKeyboard.
Defaults to false.
final bool synthesized;