code: function isKeypressCommand(nativeEvent) {
    return (nativeEvent.ctrlKey || nativeEvent.altKey || nativeEvent.metaKey) &&
    // ctrlKey && altKey is equivalent to AltGr, and is not a command.
    !(nativeEvent.ctrlKey && nativeEvent.altKey);
  }
docs: Return whether a native keypress event is assumed to be a command.
  This is required because Firefox fires `keypress` events for key commands
  (cut, copy, select-all, etc.) even though no character is inserted.