The work I've been doing for the past couple weeks can be found:
Bug 517363 - Preserve video poster aspect ratio when scaling
Bug 726904 - nsVideoFrame::GetVideoIntrinsicSize setting wrong size
Details about this one can be found in this post. Since I wrote that, I've been going back and forth with proposed patches, trying to get things working just right. It's not quite done yet, and it seems to be breaking ref-tests, so I'm going to apply for level one commit access so that I can push patches up and have the tests run on them.
This has been an interesting bug to work on, mainly because I'm modifying code in order to bring Firefox up to par with the spec. You can read more about this bug here. I've Had a lot of back and forth on this one as well, working to make sure it's up to par. I've got the fix ready to go, I just need to polish off a couple tests to make sure it doesn't break.