Comment 2 for bug 513133

Just by way of explaining what it does now, not necessarily what needs to be done to fix this bug:

It calls xdg-settings (/usr/lib/chromium-browser/xdg-settings) to check if it's the default. In the GNOME environment, it will check /desktop/gnome/applications/browser, /desktop/gnome/url-handlers/http, and /desktop/gnome/url-handlers/https as well as call "xdg-mime query defaults text/html" which checks /usr/share/applications/defaults.list. So at least all 3 of those must be set correctly. And for the gconf keys, it must be the full path to the executable.