Responsive placeholder

[danirabbit]

Problem

Granite.Placeholder is great as a welcome screen or as a placeholder in large lists, but for smaller lists in dialogs and popovers it is way too big

Proposal

An alternate, more compact style. Maybe we can do this automatically if the placeholder is inside a popover or dialog and/or with a style class?

Prior Art (Optional)

In this popover in Mail we make our own custom placeholder because Granite's is too big

[danirabbit]

Think about it more, I think it should just automatically scale based on its parent. So for example:

list placeholder .title-1 {
    font-size: 2em;
}

list placeholder .title-2 {
    font-size: 1em;
}

popover placeholder > grid > .large-icons {
    -gtk-icon-size: 32px;
}

popover placeholder .title-1 {
    font-size: 1em;
}

popover placeholder .title-2 {
    font-size: 0.85em;
}