See also .loading-icon -- a similar one for links. Current one is for buttons.
See also .strut and how it's being used on a search page over the map.
Default version is transparent.
With background:
If there is no text just remove .loading-bar__label from DOM:
For no spinner case remove .loading-bar__spinner from DOM:
In order to stretch the component add style="width: 300px;"
Alternatively set a width on a parent. For example, it is 100% on a .strut