Give descendants of cr.ui.ListItem a unique ID to fix accessibility.

ui/file_manager/integration_tests/file_manager/create_new_folder.js

Index: ui/file_manager/integration_tests/file_manager/create_new_folder.js
diff --git a/ui/file_manager/integration_tests/file_manager/create_new_folder.js b/ui/file_manager/integration_tests/file_manager/create_new_folder.js
index 7c74d968309f2318a29064e05965fb8b256e2523..84642ed1c97c78753b2f39fdad2903a7c71d2b7a 100644
--- a/ui/file_manager/integration_tests/file_manager/create_new_folder.js
+++ b/ui/file_manager/integration_tests/file_manager/create_new_folder.js
@@ -47,7 +47,7 @@ function selectFirstListItem(windowId) {
         ['div.detail-table > list > li[selected]']);
   }).then(function(elements) {
     chrome.test.assertEq(1, elements.length);
-    chrome.test.assertEq('detail-table-1', elements[0].attributes['id']);
+    chrome.test.assertEq('listitem-1', elements[0].attributes['id']);
   });
 }