Add class to allow for overriding scrollbar width

Closes #1379

(cherry picked from commit 42343d528372c494b297e5c84125f7bdb6ab4eec)

frontend/src/Components/Scroller/OverlayScroller.css

@@ -2,6 +2,10 @@
   /* Placeholder */
 }
 
+.track {
+  /* Placeholder */
+}
+
 .thumb {
   min-height: 100px;
   border: 1px solid transparent;

frontend/src/Components/Scroller/OverlayScroller.js

@@ -64,6 +64,7 @@ class OverlayScroller extends Component {
 
     return (
       <div
+        className={styles.track}
         style={finalStyle}
         {...props}
       />
@@ -82,6 +83,7 @@ class OverlayScroller extends Component {
 
     return (
       <div
+        className={styles.track}
         style={finalStyle}
         {...props}
       />