Show correct warning in non firefox browsers (#2947)
Show correct warning in non firefox browsers (#2947)

- fixes #2942
meandavejustice/testpilot,mozilla/idea-town-server,lmorchard/idea-town-server,fzzzy/testpilot,lmorchard/idea-town,mozilla/idea-town-server,mozilla/idea-town,meandavejustice/testpilot,mozilla/idea-town-server,mozilla/idea-town,flodolo/testpilot,lmorchard/idea-town-server,lmorchard/idea-town-server,lmorchard/testpilot,lmorchard/idea-town-server,lmorchard/testpilot,mozilla/idea-town,flodolo/testpilot,fzzzy/testpilot,chuckharmston/testpilot,lmorchard/idea-town,chuckharmston/testpilot,meandavejustice/testpilot,mozilla/idea-town-server,lmorchard/idea-town,fzzzy/testpilot,lmorchard/idea-town,flodolo/testpilot,chuckharmston/testpilot,mozilla/idea-town,chuckharmston/testpilot,flodolo/testpilot,fzzzy/testpilot,lmorchard/testpilot,meandavejustice/testpilot,lmorchard/testpilot