Dialog: Fixed #4015: Set z-index on shadow when the dialog opens.

ui/ui.dialog.js

@@ -210,6 +210,7 @@ $.widget("ui.dialog", {
 		this._size();
 		this._position(options.position);
 		uiDialog.show(options.show);
+		(options.shadow && this._createShadow());
 		this.moveToTop(true, event);
 
 		// prevent tabbing out of modal dialogs
@@ -244,8 +245,6 @@ $.widget("ui.dialog", {
 			.filter(':first')
 			.focus();
 
-		(options.shadow && this._createShadow());
-
 		this._trigger('open', event);
 		this._isOpen = true;
 	},