Ticket #35826: 35826.patch

wp-admin/css/customize-controls.css

@@ -795 +795 @@
         min-height: 40px;
 }
 
+.placeholder{
+        border: 1px dashed #ccc;
+        box-sizing: border-box;
+        height: 40px !important;
+}
+
 .customize-control-media .placeholder,
 .customize-control-upload .placeholder,
 .customize-control-image .placeholder,