a11y/options: Fix initial tab focus bug on supervised user history page.

chrome/test/data/webui/history_browsertest.js

Index: chrome/test/data/webui/history_browsertest.js
diff --git a/chrome/test/data/webui/history_browsertest.js b/chrome/test/data/webui/history_browsertest.js
index ae779c666de44c2b6ce007c7b1cf674388a5d49f..96891840fe658e797b7f62f035dfe0f34abbf87d 100644
--- a/chrome/test/data/webui/history_browsertest.js
+++ b/chrome/test/data/webui/history_browsertest.js
@@ -777,6 +777,11 @@ TEST_F('HistoryWebUIRealBackendTest', 'basic', function() {
   testDone();
 });
 
+TEST_F('HistoryWebUIRealBackendTest', 'atLeastOneFocusable', function() {
+  assertEquals(1, document.querySelectorAll('[tabindex="0"]').length);
+  testDone();
+});
+
 /**
  * Test individual deletion of history entries.
  */
@@ -862,6 +867,11 @@ TEST_F('HistoryWebUIDeleteProhibitedTest', 'deleteProhibited', function() {
   waitForCallback('deleteFailed', testDone);
 });
 
+TEST_F('HistoryWebUIDeleteProhibitedTest', 'atLeastOneFocusable', function() {
+  assertEquals(1, document.querySelectorAll('[tabindex="0"]').length);
+  testDone();
+});
+
 /**
  * Fixture for History WebUI testing IDN.
  * @extends {BaseHistoryWebUITest}