[webcomponents] The order of tree of trees is not well defined when one node is not inside a shadow tree (#302)

The ordering of trees A and B when they don't share the same parent is defined as follows:
> A comes before B if the shadow host which hosts A is preceding the shadow host which hosts B.

However, when either A or B is not inside a shadow tree but the other one is, the ordering is not well defined.  I think we need to refrain from using the term "shadow host" here and instead refer to the root node of the node tree that contains A or B.

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/302