These are the places where such operations are mentioned in the spec:
1) create an element for a token
This is at least making one test fail in custom-elements/parser/parser-sets-attributes-and-children.html and causing the ASSERT in bug 187802.
2) insert a foreign element
This is at least making another test fail custom-elements/parser/parser-sets-attributes-and-children.html.
3) Operations, attributes, setters, or deleters annotated with the [CEReactions] extended attribute
Hopefully, we already do all the necessary calls, but bug 187851 will make sure we don't miss anything.
We need to be very careful with respect to how this work affects perf.
We don't really need a meta bug like this separate from the bug 154907.
*** This bug has been marked as a duplicate of bug 154907 ***