Instead of a single boolean for inside a flow thread or not, I'm changing it to be a state so that we can know if we're inside an in-flow or out-of-flow flow thread. This is important for distinguishing between the two, since in the in-flow case content can escape, so we're going to have to clear the bit and do some more work to keep it up-to-date.
Created attachment 190817 [details]
Comment on attachment 190817 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=190817&action=review
> + unsigned m_flowThreadState : 2; // FlowThreadState
There's a comment above about the number of remaining bits that should be updated.
Landed in r144461.