Reduce window title bars height in Ubuntu

When you enable scaling in Ubuntu, window's title bars are absurdly big. It is relatively easy to fix by just modifying the gtk theme.

~/.config/gtk-3.0/gtk.cs (create if does not exist)

/* shrink headerbars (don't forget semicolons after each property) */
headerbar {
    min-height: 0px;
    padding-left: 2px; /* same as childrens vertical margins for nicer proportions */
    padding-right: 2px;
    background-color: #2d2d2d;
}

headerbar entry,
headerbar spinbutton,
headerbar button,
headerbar separator {
    margin-top: 0px; /* same as headerbar side padding for nicer proportions */
    margin-bottom: 0px;
}

/* shrink ssd titlebars */
.default-decoration {
    min-height: 0; /* let the entry and button drive the titlebar size */
    padding: 0px;
    background-color: #2d2d2d;
}

.default-decoration .titlebutton {
    min-height: 0px; /* tweak these two props to reduce button size */
    min-width: 0px;
}

window.ssd headerbar.titlebar {
    padding-top: 3px;
    padding-bottom: 3px;
    min-height: 0;
}

window.ssd headerbar.titlebar button.titlebutton {
    padding: 3px;
    min-height: 0;
}