Change the default theme to differentiate from 4.8

themes/default/close-active.png

themes/default/close-active.svg

themes/default/close-inactive.png

themes/default/close-inactive.svg

themes/default/close-prelight.png

themes/default/close-prelight.svg

themes/default/close-pressed.png

themes/default/close-pressed.svg

themes/default/hide-active.png

themes/default/hide-active.svg

themes/default/hide-inactive.png

themes/default/hide-inactive.svg

themes/default/hide-prelight.png

themes/default/hide-prelight.svg

themes/default/hide-pressed.png

themes/default/hide-pressed.svg

themes/default/maximize-active.png

themes/default/maximize-active.svg

themes/default/maximize-inactive.png

themes/default/maximize-inactive.svg