Onion sites circuits are not properly isolated to URL bar domain
As mentioned on IRC, s7r's test case and results are:
I have setup an .onion which loads an image from another onion. it creates 2 circuits but it's smart enough when I access the second onion where the resources are loaded from, it uses the same circuit used to load the resources initially.
This seems not the thing we want. As mikeperry noted we want to have the access to the second onion over a different circuit than loading the resources while accessing onion 1.
This might actually require a Tor patch (too).