Changes

** <strike>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.</strike>*** Incorrect. John J Barton points out that a typical web apps log hundreds of messages and most of them are ignored. We can hold off fetching the source map until the user first requests it by trying to display more information about a particular logged message or error thrown. Until that point in time, the source map information is useless because in all likelihood the user isn't even looking at it.