Test that DevTools commands can be handled on worker thread when it is in a tight loop

The new test checks that when worker thread is blocked on a tight loop in JavaScript it can be interrupted to handle pending DevTools commands.

BUG=340522

Review URL: https://codereview.chromium.org/352103002

git-svn-id: svn://svn.chromium.org/blink/trunk@176916 bbb929c8-8fbe-4397-9dbb-9b2b20218538