wp-calypso/client/components/async-load/style.scss

.async-load__placeholder {
	background: var(--color-neutral-10);
	border-radius: 20px; /* stylelint-disable-line scales/radii */
	content: "";
	display: block;
	height: 8px;
	width: 80px;
	margin: 0 16px;
	animation: pulse-light 0.8s ease-in-out infinite;
}