DevTools: repair WorkerDevToolsSanityTest.InspectSharedWorker browser test

It was broken in https://chromium.googlesource.com/chromium/blink/+/30f11148be4ef1037f311e86a7707396e457d429%5E%21/#F13

BUG=89845,403007

Review URL: https://codereview.chromium.org/655203002

git-svn-id: svn://svn.chromium.org/blink/trunk@183742 bbb929c8-8fbe-4397-9dbb-9b2b20218538