Log actual data loaded.

Just want to give you something to look at before I go to bed. :)

After creating the stream listener, I discovered it didn't work with local files (or things like `about:`). "Life-of-request info" (lori) did, and it just used a progress listener. Turns out adding the listener to the *browser* works just fine. Atm it still uses `onDataAvailable`, but I think switching to `onProgressChange` would be better (losing the difference between network & cache, but data is uncompressed size, whereas progress is compressed). Alternatively, keep 'em all, creating a replacement for the Web Developer/FireBug/ySlow info (although I've only looked at the first of those).