Prevented tests from taking window focus on OS X
Prevented tests from taking window focus on OS X

Prevented tests from taking window focus on OS X by explicitly requiring
them to be headless in the POM.

CIRDLES/ET_Redux,bowring/ET_Redux,CIRDLES/ET_Redux,CIRDLES/ET_Redux,bowring/ET_Redux,johnzeringue/ET_Redux,clementparizot/ET_Redux,johnzeringue/ET_Redux,bowring/ET_Redux,clementparizot/ET_Redux