When a revision is committed that only changes test files, the build.webkit.org builders first build the change, then the build.webkit.org testers download that build and test it. It's silly for the builders to build in this case, since no source files have changed. It would be better and faster if the builders would just skip this revision and the testers would use the last build the builders produced to test with.
<rdar://problem/9281203>