This is first part in a series that implements Cycle Collection for every mshtml object (dispex) and cleans up rest of the code based on it, which is obviously needed due to dynamic props and other extra object-specific refs.
In an effort to split it up as much as possible, since it already has quite a lot of restructuring and changes, some of the earlier patches will introduce temporary leaks or cyclic refs, but that's because we'll later handle them properly with the dispex CC. These shouldn't affect behavior, though, so it shouldn't pose problems for functionality.
Nodes are, initially, not changed much (other than to make it compatible with the dispex) to keep changes as small as possible. They still use their own CC mechanism and refcounting, which is hackish but that is solved in a follow-up MR, so it's temporary only.
Eventually, every object (including nodes) will use the dispex's vtbl to do its Cycle Collection, except for stuff like outer window (which is a special case).
In this first part, the objects that are using the node CC will have no-op dispex CC methods since they are using the node's, but this is temporary only.