We call disableDefaultModes  when we got Face Tracking call backs or on Touch event receive for touch Focus.

Camera.prototype.disableFocus = function() {
  this.disableContinuousFocus();
  this.disableFaceTracking();
  this.disableAutoFocus();
};
Some of the devices won't support face tracking and continuous Auto focus.
That's why we are maintaining the list of supported focus modes in 
CameraController.prototype.configureFocus () and creating object with enable and disable function.