MD Settings: Fix CrSettingsPeoplePageSyncPageTest.SyncPage test when Vulcanized.

chrome/test/data/webui/settings/people_page_sync_page_test.js

Index: chrome/test/data/webui/settings/people_page_sync_page_test.js
diff --git a/chrome/test/data/webui/settings/people_page_sync_page_test.js b/chrome/test/data/webui/settings/people_page_sync_page_test.js
index b8cd5c48b887e581507ddeced25f19dbf6f08b1e..ff1d7843ff7cd60200134e6a7c2e973f167d07d3 100644
--- a/chrome/test/data/webui/settings/people_page_sync_page_test.js
+++ b/chrome/test/data/webui/settings/people_page_sync_page_test.js
@@ -274,6 +274,9 @@ cr.define('settings_people_page_sync_page', function() {
         // on a background tab (which has throttled timers) and will timeout.
         link.target = '';
         link.href = '#';
+        // Prevent the link from triggering a page navigation when tapped.
+        // Breaks the test in Vulcanized mode.
+        link.addEventListener('tap', function(e) { e.preventDefault(); });
 
         MockInteractions.tap(link);