pculture/miro — comment on commit 311596857e249ffcf57ca4bf06d2b01cf83605b2
File: tv/windows/plat/frontends/widgets/XULRunnerBrowser/MiroWindowCreator.cpp line 119
By bendk:

You can use do_QueryInterface() to get the return value directly:

*_retval = do_QueryInterface(newWindow);

or maybe you need:

nsCOMPtr thing = doQueryInterface(newWindow);
_retval = thing;