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'