This is the one feature that is sorely missing in an app that several years into its development, remains unstable. How many times have you lost a forum post or email you were composing because Firefox crashed? Sure, you can first compose it in a text editor and then copy it over, but that's not how things are meant to be, is it?
So what we need is what every unstable word processing app now has: document recovery (Vim 6 also has this, in spite of being stable) for text fields. My suggestion would be to present it as a scrapbook, the way clipboard managers usually work.