Merge pull request #3319 from weseek/imprv/preview-layout-in-edit-mode

change scroll position

src/client/styles/scss/_on-edit.scss

@@ -232,12 +232,13 @@ body.on-edit {
     }
 
     .page-editor-preview-container {
+      overflow-y: scroll;
     }
 
     .page-editor-preview-body {
       max-width: 980px;
       padding: 18px 15px 0;
-      overflow-y: scroll;
+      margin: 0 auto;
     }
 
     .grw-editor-configuration-dropdown {