Index: style.css
--- wp-content\themes\twentyfifteen\style.css Base (BASE)
+++ wp-content\themes\twentyfifteen\style.css Locally Modified (Based On LOCAL)
@@ -899,6 +899,7 @@
 	content: "\f419";
 	line-height: 42px;
 	position: relative;
+	font-size: 32px;
 	top: -1px;
 	left: 0;
 }
@@ -913,7 +914,6 @@
 
 .secondary-toggle.toggled-on:before {
 	content: "\f405";
-	font-size: 32px;
 	top: 0;
 	left: -1px;
 }