Pixel results for fast/canvas/canvas-before-css have changed (see URL), presumably because of <http://trac.webkit.org/projects/webkit/changeset/19687>.
Also caused many failures in svg tests, e.g. <http://build.webkit.org/results/post-commit-pixel-powerpc-mac-os-x/3666/svg/custom/js-late-pattern-creation-diffs.html>
Fixed by Hyatt in <http://trac.webkit.org/projects/webkit/changeset/19851>.