fix(overlay): wrap class addition in RAF #9882

Author: PlamenaMiteva

projects/igniteui-angular/src/lib/services/overlay/overlay.ts

@@ -707,7 +707,9 @@ export class IgxOverlayService implements OnDestroy {
         //  to eliminate flickering show the element just before animation start
         info.wrapperElement.style.visibility = '';
         info.visible = true;
-        this.addModalClasses(info);
+        requestAnimationFrame(() => {
+            this.addModalClasses(info);
+        });
         info.openAnimationPlayer.play();
     }