Favorite text editor in web browser

I spend a lot of time on the read-write web. I work on a lot of large complicated documents on the web. I often copy text from forms in my web browser to a text editor that is easy to use. I am sick of using basic text editors that web browsers have. This however is a less than ideal workflow.

I would love to have my favorite text editor embedded in my favorite web browser. Something like this:
composed screenshot showing textmate embedded in firefox