adoptNode() should always return a node

[TRowbotham]

In the adoptNode() steps, step 3 says "If node is a DocumentFragment node whose host is non-null, then return.", but the interface defines adoptNode() as always returning a node. Shouldn't step 3 either return node or throw, or am I missing something from IDL that would allow returning nothing?

[annevk]

See #819.

[TRowbotham]

I clearly forgot to use the search function, thanks for the context and sorry for the noise