Embeds width is 300 in latest trunk

Hello,

I think I may have come across a regression in the latest nightly build.

I'm using the following url on it's own line to embed a video from Youtube:

http://youtu.be/D7JB68sLGY8

Here's a screenshot from trunk:
https://img.skitch.com/20120422-pwsf6cmjgyns2bhsa49pnsh3cq.png

And one from 3.3.1:
https://img.skitch.com/20120422-cuncch5qykhhjyh6s7b1uhxug4.png

Notice how the trunk embed appears at a width of 300px while the 3.3.1 
example appears at a width of 584px.

584 is the value of the $content_width global which seems to be ignored 
in trunk.

I've tested with Twenty Eleven as well as a few other themes that I have 
installed locally and the results were the same as outlined above.

Best,
-Mike