Diagnose problems with "steam:" URL handler
Now we are able to diagnose if there are problems with how we handle the
steam://
URLs.
This MR includes the commit from !116 (merged) . Even if this new feature is not really tight to the other one, I created them one on top of the other so it was easier to leave them as is instead of separating them and resolve the merge conflicts afterwards.
/cc @smcv @jpwhiting