DevTools fail to load external sourcemaps

DevConsole does not load external source maps, i.e. referenced via `//# sourceMappingURL= `. Chrome works fine with those files. In Falkon I get the following message "DevTools failed to parse SourceMap: <correct and clickable URL>". 

Source maps do not work unless I include sources in it. So I have to a) create fat source maps with embedded sources and b) include them via data-urls. Chrome needs neither a) nor b) for source maps to work.

I added a print statement `Common.console.log(e.name + ': ' + e.message);` to the `SourceMapManager.attachSourceMap()` and it prints out: "Error: Could not load content for <a correct sourcemap uri> : HTTP status code: 200". One of my script libs contains a reference to an absent source map file, and the exception for it is the same ("Could not load content...").