Fix potential flakiness in Files.app test

ui/file_manager/integration_tests/file_manager/tab_index.js

Index: ui/file_manager/integration_tests/file_manager/tab_index.js
diff --git a/ui/file_manager/integration_tests/file_manager/tab_index.js b/ui/file_manager/integration_tests/file_manager/tab_index.js
index fd7ae6e0ddbe1a77c233d7bbfabb413ba168f73b..214f2b6ea2496738d5e8bbf8166fb1b8cb0abe83 100644
--- a/ui/file_manager/integration_tests/file_manager/tab_index.js
+++ b/ui/file_manager/integration_tests/file_manager/tab_index.js
@@ -66,9 +66,12 @@ testcase.tabindexFocus = function() {
       appId = inAppId;
       remoteCall.waitForElement(appId, ['#file-list:focus']).then(this.next);
     },
-    // Press the Tab key.
+    function(element) {
+      remoteCall.waitForElement(appId, ['#drive-welcome-link']).then(this.next);
+    },
     function(element) {
       remoteCall.callRemoteTestUtil('getActiveElement', appId, [], this.next);
+    // Press the Tab key.
     }, function(element) {
       chrome.test.assertEq('list', element.attributes['class']);
       remoteCall.checkNextTabFocus(appId, 'search-button').then(this.next);
@@ -150,7 +153,9 @@ testcase.tabindexFocusDirectorySelected = function() {
       appId = inAppId;
       remoteCall.waitForElement(appId, ['#file-list:focus']).then(this.next);
     },
-    // Press the Tab key.
+    function(element) {
+      remoteCall.waitForElement(appId, ['#drive-welcome-link']).then(this.next);
+    },
     function(element) {
       remoteCall.callRemoteTestUtil('getActiveElement', appId, [], this.next);
     }, function(element) {
@@ -158,6 +163,7 @@ testcase.tabindexFocusDirectorySelected = function() {
       // Select the directory named 'photos'.
       remoteCall.callRemoteTestUtil(
           'selectFile', appId, ['photos']).then(this.next);
+    // Press the Tab key.
     }, function(result) {
       chrome.test.assertTrue(result);
       remoteCall.checkNextTabFocus(appId, 'share-button').then(this.next);