Breakpoint locations after hot-restart

[elliette]

Steps to reproduce:

1. Set a breakpoint on a line, e.g. line 10
2. Edit the file that contains that breakpoint so that the breakpoint location should be moved (e.g. add a new line above line 10, so the breakpoint should now be at line 11)
3. Hot-restart the app

The breakpoint will stay at the old location (line 10) when it should now be at line 11