pretty diff: http://build.webkit.org/results/Qt%20Linux%20Release/r81235%20(29890)/inspector/elements/mutate-unknown-node-pretty-diff.html
I added it to the Skipped list: http://trac.webkit.org/changeset/81239
This just failed on Windows, too: http://build.webkit.org/results/Windows%20XP%20Debug%20(Tests)/r81480%20(26521)/inspector/elements/mutate-unknown-node-pretty-diff.html
I will remove the test from the Qt Skipped list and just disable it for now.
Disabled the test in http://trac.webkit.org/changeset/81488
<rdar://problem/9155306>
Closing as invalid, as this bug pertains to the old inspector UI and/or its tests. Please file a new bug (https://www.webkit.org/new-inspector-bug) if the bug/feature/issue is still relevant to WebKit trunk.