In r54084 I've noticed that the page down key does not scroll by a constant amount on each press. The first press scrolls by approximately 5 lines, the second by 35. This works correctly in a build of WebKit from earlier in the week.
Regression from the switch to canvas based source view.
<rdar://problem/7594369>
Fixed in http://trac.webkit.org/changeset/54133.
(https://bugs.webkit.org/show_bug.cgi?id=34400 - bug reference was missing due to prepareChangeLog bug).