Adding JS and C++ handlers for events on new Welcome page.

chrome/browser/resources/welcome/welcome.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(tmartino): Add handlers.
-console.log('JS test');
+document.addEventListener('DOMContentLoaded', function() {

[anthonyvd, 2016/09/19 17:12:15]

You can take a look at
https://cs.chromium.org/chromium/src/chrome/browser/resources/signin/sync_con...
for the canonical way of doing js setup (using cr.define and all that jazz).

+  $('accept_button').addEventListener('click', function() {
+    chrome.send('handleActivateSignIn');
+  });
+
+  $('decline_button').addEventListener('click', function() {
+    chrome.send('handleUserDecline');
+  });
+});