DevTools: follow up to r165291, fix WorkerDevToolsSanityTest.InspectSharedWorker
TBR=alph

Review URL: https://codereview.chromium.org/141663002

git-svn-id: svn://svn.chromium.org/blink/trunk@165302 bbb929c8-8fbe-4397-9dbb-9b2b20218538