When calling FrameQtClient::openUrl for the first time, the owned frames doesn't have a document set on it at all. In turn ResourceLoader depends on the DocumentLoader in order to work and Qt's ResourceLoaderManager depends on it being present in order to set Frame (in order to call checkLoaded). openUrl used to let through creation of ResourceLoader with no parent document which causes crashes due to above described dependencies. The patch explictly creates an empty document if one isn't already present.
Created attachment 11237 [details] Mentioned patch to fix the crash.
Created attachment 11288 [details] Updated patch with ChangeLog
Comment on attachment 11288 [details] Updated patch with ChangeLog r=me
This was landed by Anders in r17441.