Missing indicator for worker status

This tests that developers are able to tell the status of a worker by looking at the Threads view in the DevTools.

Steps

1. Open DevTools
2. Reload the page
3. Look at the Threads view in the Sources / Debugger panel, and discover Main is shown as idle, while worker-status-busy.js is shown as actively executing, while worker-status-wait.js is shown as waiting in Atomics.wait