Tests depending on it fail. They work using a timer to wait for the scroll to happen.
fast/scrolling/scroll-container-horizontally.html is mostly passing now since r227966, but the test still fails sometimes. Updating expectations accordingly.
There are no references to this bug in any TestExpectations. It's probable this bug was solved at some point but it wasn't marked as closed. I'm closing this bug now. If you think this bug report is still valid, please reopen it and add an entry to TestExpectations.