Webkit/Chromium/Chrome's project development process is interesting. From what I've seen on the bug trackers, whenever a piece of code (no matter what size) causes any sort of stability/performance regression at all, the patches committing it are aggressively backed out and dropped on the floor, with the expectation that whoever cared enough to commit them in the first place will realize their code was pulled, fix it, and re-commit.

This causes features to sometimes just "go missing" for long periods of time, if the original committer (i.e. the code's only advocate with commit privs) A. works for some big company that's not Google or Apple, and thus has other responsibilities; B. was just "helpfully" pushing the code they wrote for their own private fork of Webkit/Chromium; and C. doesn't much care what happens to it in the OSS project after that.