wp-calypso/packages/block-renderer/src/components/block-renderer-container.scss

.block-renderer {
	position: relative;
	width: 100%;
	overflow: hidden;

	.scaled-block-renderer {
		top: 0;
		left: 0;
		transform-origin: top left;
		text-align: initial;
		margin: 0;
		overflow: visible;
		min-height: auto;
		transform: scale(var(--scaled-block-renderer-scale, 1));

		iframe {
			max-width: initial;
			border: none;
			// Overwrites the inlined transition: all 0.3s ease 0s; from Gutenberg
			transition: opacity 0.15s ease-in-out !important;
		}
	}
}