If true the .children property will always be sorted in the z-index ordering.
Also, the appendChild method will append the children in the top-most position.
The insertChild method is changed accordingly to respect this ordering.
Defaults to false
If true the validation errors will throw an exception instead of displaying an
error in the debugger console.
Defaults to true for plugins whose manifest declares "version": 2 (or higher)
and to false for v1 plugins (or manifests that omit the version field).
This subcontext allows the API to change certain defaults