[MOB-4840] Fix iframe height setting (#155)

* [MOB-4840] Fix iframe height setting

* [MOB-4840] Add comment

Author: pauljung14

src/inapp/utils.ts

@@ -423,8 +423,15 @@ export const paintIFrame = (
         };
 
         if (position !== 'Full') {
+          const iframeHeight =
+            iframe.contentWindow?.document?.body?.scrollHeight;
+          /*
+            For web in-app messages created with WYSIWYG editor,
+            there is 8px margin all around the iframe document body.
+            Add 16px to the iframe height to eliminate scrollbar.
+          */
           iframe.style.height =
-            (iframe.contentWindow?.document?.body?.scrollHeight || 0) + 'px';
+            ((iframeHeight && iframeHeight + 16) || 0) + 'px';
         }
 
         clearTimeout(timeout);