Plank tooltips don't have box shadow

[Danielle Foré]

Looks like the box-shadow for the selector "tooltip" or ".toolip" isn't applied.

For future proofing, after gtk 3.20, there is a selector "tooltip decoration" for shadows.

More specfically this is the CSS I'm currently using for Gtk 3.18 and Gtk 3.20:

tooltip,
tooltip.background,
.tooltip,
.overlay-bar {
    background-color: alpha (#333, 0.8);
    border-radius: 3px;
    border-width: 0;
    box-shadow: 0 1px 3px alpha (#000, 0.12),
                0 1px 2px alpha (#000, 0.24);
    padding: 3px 6px;
    margin: 6px;
    text-shadow: 0 1px 2px alpha (#000, 0.6);
}

tooltip decoration {
    border-radius: 3px;
    box-shadow: 0 1px 3px alpha (#000, 0.12),
                0 1px 2px alpha (#000, 0.24);
    margin: 0;
}