Test that setting and getting justify-content works as expected


PASS Test getting justify-content values previously set through CSS. 
PASS Test setting invalid values to justify-content through CSS. 
PASS Test initial value of justify-content through JS 
PASS Test getting and setting justify-content through JS 
PASS Test bad combinations of justify-content 
PASS Test the value 'initial' 
PASS Test the value 'initial' for grid containers 
PASS Test the value 'initial' for flex containers 
PASS Test the value 'inherit'