Nit, but confused me for a minute.

https://docs.flutter.io/javadoc/io/flutter/plugin/common/PluginRegistry.RequestPermissionResultListener.html

This offers onRequestPermissionResult, which I believe is supposed to wrap the system or compat method, which is https://developer.android.com/reference/android/support/v4/app/ActivityCompat.OnRequestPermissionsResultCallback.html#onRequestPermissionsResult(int, java.lang.String[], int[]) onRequestPermissionsResult - note Permissions is plural, not singular. Should probably be that way across the board.