Restore optSelected hack still needed by IE9/10

src/attributes.js

@@ -478,3 +478,17 @@ jQuery.each([ "radio", "checkbox" ], function() {
 		}
 	});
 });
+
+// IE9/10 do not see a selected option inside an optgroup unless you access it
+// Support: IE9, IE10
+if ( !jQuery.support.optSelected ) {
+	jQuery.propHooks.selected = jQuery.extend( jQuery.propHooks.selected, {
+		get: function( elem ) {
+			var parent = elem.parentNode;
+			if ( parent && parent.parentNode ) {
+				parent.parentNode.selectedIndex;
+			}
+			return null;
+		}
+	});
+}

src/support.js

@@ -47,6 +47,10 @@ jQuery.support = (function() {
 		// Check the default checkbox/radio value ("" on WebKit; "on" elsewhere)
 		checkOn: !!input.value,
 
+		// Must access the parent to make an option select properly
+		// Support: IE9, IE10
+		optSelected: opt.selected,
+
 		// Makes sure cloning an html5 element does not cause problems
 		// Where outerHTML is undefined, this still works
 		html5Clone: document.createElement("nav").cloneNode( true ).outerHTML !== "<:nav></:nav>",