Merge remote-tracking branch 'origin/MAGETWO-46727' into PR-2

Author: Natalia Momotenko

app/design/adminhtml/Magento/backend/Magento_Ui/web/css/source/module/_data-grid.less

@@ -7,13 +7,6 @@
 //  UI -> Data Grid
 //  _____________________________________________
 
-//
-//  Variables
-//  ---------------------------------------------
-
-@data-grid-sticky-header__z-index: @page-actions__fixed__z-index;
-@data-grid-overlay__z-index: @data-grid-sticky-header__z-index + 1;
-
 //
 //  Components
 //  ---------------------------------------------

app/design/adminhtml/Magento/backend/web/css/source/variables/_structure.less

@@ -26,13 +26,15 @@
 @action-multicheck__z-index: @z-index-2;
 
 //  z-index 3
-@actions-split__z-index: @z-index-3;
 @data-grid-header__z-index: @z-index-3;
 
 //  z-index 4
 @header__z-index: @z-index-4;
 @page-actions__fixed__z-index: @z-index-4;
 @data-grid-overlay__z-index: @z-index-4;
+@data-grid-sticky-header__z-index: @page-actions__fixed__z-index - 2;
+@data-grid-overlay__z-index: @data-grid-sticky-header__z-index + 1;
+@actions-split__z-index: @data-grid-overlay__z-index + 1;
 
 //  z-index 5
 @field-tooltip__z-index: @z-index-5;