keyEventHandled method
Indicates that the key event received by onKeyEvent is handled.  This
should only be called if the onKeyEvent listener is asynchronous.
requestId Request id of the event that was handled.  This should come
from keyEvent.requestId
response True if the keystroke was handled, false if not
Implementation
void keyEventHandled(
  String requestId,
  bool response,
) {
  $js.chrome.input.ime.keyEventHandled(
    requestId,
    response,
  );
}