This is a meta bug for refactoring FrameLoader. You can add yourself to the CC list of you'd like to follow our progress.
Nate and I are working out a plan for making the loader more sane. Our working diagram is here: https://docs.google.com/drawings/edit?id=1V3JZltHfNU0HN9bPlLrHOC_yYTriPgv4Dv-LRamymFU&hl=en It's very incomplete at the moment. We're still trying to understand what problem each object solves and what the separate concerns are.