Fix visualiser shaking

Summary:
Fixes https://fb.workplace.com/groups/443457641253219/permalink/731880702410910/

There was an issue with the visualisers resizing repeatidly as the scrollbar came in at a certain point. Simple solution is to have it always shown, to maximise space we make the scrollbar style thing

Changelog: UIDebugger fix visualiser shaking

Reviewed By: antonk52

Differential Revision: D55696687

fbshipit-source-id: 1f9cba35993c31679179890e6ecbd2830b60e400

desktop/plugins/public/ui-debugger/components/visualizer/Visualization2D.tsx

@@ -103,7 +103,7 @@ export const Visualization2D: React.FC<
   );
 };
 
-const horizontalPadding = 16; //allows space for vertical scroll bar
+const horizontalPadding = 8; //allows space for vertical scroll bar
 
 function Visualization2DContent({
   disableInteractivity,
@@ -223,6 +223,8 @@ function Visualization2DContent({
       ref={containerRef}
       style={{
         paddingLeft: horizontalPadding,
+        overflowY: 'scroll',
+        scrollbarWidth: 'thin',
       }}
       vertical>
       <div