Currently, when debugging source-mapped scripts, the mapped variables names may not match the source variable names. Referencing these variables in the console doesn't work. Firefox DevTools has "Scopes [ ] Map" checkbox. https://developer.mozilla.org/en-US/docs/Tools/Debugger/Using_the_Debugger_map_scopes_feature We should either: - Do it like Firefox, e.g. add a on/off toggle. - Always enable it. <rdar://70778463>