Inspector front-end for dedicated worker is a child window launched with window.open(<front-end url>). After http://crrev.com/126949 we started receiving "beforeunload" event for "about:blank" page before <front-end url> page is loaded. This breaks worker front-end.
Created attachment 133756 [details] Patch
Committed r112072: <http://trac.webkit.org/changeset/112072>