Ticket #20582: 20582.preview-thumbnail.patch

wp-includes/css/customize-controls.dev.css

@@ -390 +390 @@
 
 .customize-section .customize-control-image .preview-thumbnail img {
         display: block;
+        width: 100%;
         max-width: 122px;
         max-height: 98px;
         margin: 0 auto;