Currently, caching based on structudeIDs in TypeSet is invalid because it will claim it has seen a Structure that it might not have seen. This needs to be fixed. The easiest solution is simply to clear all StructureID caches in TypeSet when we garbage collect.
Created attachment 237167 [details] patch This clears each TypeSet's StructureID cache each time GC collects. It also renamed the member variable on TypeSet to better indicate it's a cache.
Comment on attachment 237167 [details] patch r=me
Comment on attachment 237167 [details] patch Clearing flags on attachment: 237167 Committed r172976: <http://trac.webkit.org/changeset/172976>
All reviewed patches have been landed. Closing bug.