MD Settings: fix auto-focus on sync page.

chrome/browser/resources/settings/people_page/sync_page.js

Index: chrome/browser/resources/settings/people_page/sync_page.js
diff --git a/chrome/browser/resources/settings/people_page/sync_page.js b/chrome/browser/resources/settings/people_page/sync_page.js
index 8078686bd65191aa99cdd123b62bb0a8c771bf77..f40443683c14778d248e885168ac19ba116c5af8 100644
--- a/chrome/browser/resources/settings/people_page/sync_page.js
+++ b/chrome/browser/resources/settings/people_page/sync_page.js
@@ -216,8 +216,8 @@ Polymer({
 
     // Focus the password input box if password is needed to start sync.
     if (this.syncPrefs.passphraseRequired) {
-      // Async to allow the dom-if templates to render first.
-      this.async(function() {
+      // Wait for the dom-if templates to render and subpage to become visible.
+      listenOnce(document, 'show-container', function() {
         var input = /** @type {!PaperInputElement} */ (
             this.$$('#existingPassphraseInput'));
         input.inputElement.focus();