Repro for crbug.com/1229541

This tests that DevTools properly hits breakpoints when starting a worker.

Steps

1. Open DevTools
2. Set a breakpoint in crbug-1229541.js on line 1
3. Click the button to spawn a new worker, DevTools should stop on the previously set breakpoint
4. Click the button again to spawn another worker, DevTools should stop on the previously set breakpoint