Merge remote-tracking branch 'origin/MAGETWO-40062' into PR

Author: Natalia Momotenko

app/design/adminhtml/Magento/backend/web/css/source/components/_popups.less

@@ -482,6 +482,10 @@
     }
 }
 
+.ui-widget-overlay {
+    &:extend(.abs-modal-overlay all);
+}
+
 .overlay_magento {
     &:extend(.abs-modal-overlay all);
     z-index: 800 !important;