Fix a regression where all the head elements were removed since they are invisible
Fix a regression where all the head elements were removed since they are invisible

mozilla-services/screenshots,mozilla-services/screenshots,fzzzy/pageshot,mozilla-services/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/pageshot,mozilla-services/pageshot,fzzzy/pageshot,mozilla-services/pageshot