*** This neatly side-steps the above issues because if the tool isn't on, it won't ever fetch the source map.
* When should the <strike>browser </strike> debugger fetch the source map?
** As soon as it knows of the existence of the source map?
** By the time a message is logged, or an exception is thrown, it is already too late to fetch the source map because we do not want to delay displaying a message while we go fetch the source map.