Describe the bug:
After navigating to a different domain from when we connected to the DevTools server, the reloading stops working.

To Reproduce:
./mach run --devtools=6080, attach the DevTools client, and go to a different domain than servo.org. Try to reload the page through DevTools.

Platform:
Windows 10 x86_64, although it shouldn't matter in this case.

---

I noticed this problem while trying to implement "back" and "forward" buttons for #38668 and encountering the same problem. My guess is that navigating to a different domain spawns a new script thread, and so script_chan used in

to handle the reload might be outdated (i.e. sends messages to the thread that manages the pipeline for the document we navigated from, but not the one we navigated to).

Don't take my word for it though as I've only recently started contributing to Servo, so the guess might be very wrong. 😄