Ticket #35826: 35826.1.patch

wp-admin/css/customize-controls.css

@@ -806 +806 @@
         position: relative;
         text-align: center;
         cursor: default;
+        border: 1px dashed #ccc;
+        box-sizing: border-box;
+        height: 40px !important;
 }
 
 .customize-control-media .inner,