Use padding top/bottom instead of before/after for top/bottom frame

packages/block-editor/src/components/iframe/content.scss

@@ -32,11 +32,11 @@
 	$total-frame-height: calc(2 * #{$frame-size} / #{$scale});
 	$total-height: calc(#{$extra-content-height} + #{$total-frame-height} + 2px);
 	margin-bottom: calc(-1 * #{$total-height});
-
-	&::before,
-	&::after {
-		height: calc(#{$frame-size} / #{$scale});
-	}
+	// Add the top/bottom frame size. We use scaling to account for the left/right, as
+	// the padding left/right causes the contents to reflow, which breaks the 1:1 scaling
+	// of the content.
+	padding-top: calc(#{$frame-size} / #{$scale});
+	padding-bottom: calc(#{$frame-size} / #{$scale});
 
 	body {
 		min-height: calc((#{$inner-height} - #{$total-frame-height}) / #{$scale});