Set default control on Terms of Service screen

chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js

Index: chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js
diff --git a/chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js b/chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js
index b2769605168cd9e1fd4d648d772de036fb5bd848..8776629aad3d140507e3604f19402853b6548950 100644
--- a/chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js
+++ b/chrome/browser/resources/chromeos/login/oobe_screen_terms_of_service.js
@@ -37,6 +37,22 @@ cr.define('oobe', function() {
         localStrings.getStringF('termsOfServiceContentHeading', domain);
   };
 
+  /**
+   * Displays the given |termsOfService|, enables the accept button and moves
+   * the focus to it.
+   * @param {string} termsOfService The terms of service, as plain text.
+   */
+  TermsOfServiceScreen.setTermsOfService = function(termsOfService) {
+    $('terms-of-service').classList.remove('tos-loading');
+    $('tos-content-main').textContent = termsOfService;
+    $('tos-accept-button').disabled = false;
+    // Initially, the back button is focused and the accept button is disabled.
+    // Move the focus to the accept button now but only if the user has not
+    // moved the focus anywhere in the meantime.
+    if (!$('tos-back-button').blurred)

[Nikita (slow), 2013/02/12 20:51:48]

nit: You could check what's the current document.activeElement is so that you
won't need additional property (blurred).

[bartfab (slow), 2013/02/12 23:22:59]

The property actually is needed to achieve the semantics I am after: I want to
avoid changing the focus if the user has modified the focus manually in any way,
even if that included moving the focus back to the button that was focused
initially. So I do not want to find out whether the default button is focused
right now, I want to find out whether it had ever lost focus in the past.

+      $('tos-accept-button').focus();
+  };
+
   TermsOfServiceScreen.prototype = {
     // Set up the prototype chain.
     __proto__: HTMLDivElement.prototype,
@@ -61,6 +77,9 @@ cr.define('oobe', function() {
         $('tos-accept-button').disabled = true;
         chrome.send('termsOfServiceBack');
       });
+      backButton.addEventListener('blur', function(event) {
+        this.blurred = true;
+      });
       buttons.push(backButton);
 
       var acceptButton = this.ownerDocument.createElement('button');
@@ -80,6 +99,14 @@ cr.define('oobe', function() {
     },
 
     /**
+     * Returns the control which should receive initial focus.
+     */
+    get defaultControl() {
+      return $('tos-accept-button').disabled ? $('tos-back-button') :
+                                               $('tos-accept-button');
+    },
+
+    /**
      * Event handler that is invoked just before the screen is shown.
      * @param {object} data Screen init payload.
      */