Remove the base_url parameter for diff rendering.
Review Request #4476 — Created Aug. 21, 2013 and submitted
Remove the base_url parameter for diff rendering. We used to need this silly base_url parameter for rendering diffs. We used it for bits of the JavaScript. It's unused now, but we're still passing it around, so stop doing that.
Unit tests pass. Went to a few diffs, and didn't see problems.