Larger changesets cause view screen to become unresponsive (BB-1802)

Example: https://bitbucket.org/saintnicster/radar/changeset/a69568bc9c74

When viewing the page, the javascript used to highlight the - and + lines is causing the page to become unresponsive (unable to scroll down the page). Commit is a text commit, so the changeset screen tries to view all changes. When running in FF or IE, a popup is displayed saying that the script has become unresponsive (screenshot attached). After clicking "stop script," I am able to scroll the page again. No highlighting appear on the large entry.

Tested in Chrome 12.0.742.122, FF 5.0, IE 8.0.7600.16385