We're trying to start using cc property trees in Blink, and it would be great if we could clean up the real root (0) and secondary root (1) semantics.

Effect trees expect 0 to be a dummy unused node (an extra root) and 1 the real root, but some other trees expect 1 to be a child of 0 (but 1 to be the logical root of content), etc. It's not super clear what Blink must do here.

It would be great if this was consistent and commented. Thanks. :D