Seems we should have a tool which validates that the license blocks at the top of our header and .cpp files. This could be used in conjunction with check-webkit-style for validating patches so that reviewers don't have to.
This came up when viewing bug 27424.
*** Bug 35465 has been marked as a duplicate of this bug. ***
check-webkit-style should just do this. This comes up somewhat frequently. https://bugs.webkit.org/show_bug.cgi?id=73559#c12 is where I saw a license issue today.