Separate out logic in initialisation code to help in separating native vs non-native code paths when supporting document.registerElement.
Separate out logic in initialisation code to help in separating native vs non-native code paths when supporting document.registerElement.

skatejs/skatejs,skatejs/skatejs,chrisdarroch/skatejs,skatejs/skatejs,antitoxic/skatejs,chrisdarroch/skatejs