Adding client code for new Windows 10 First Run Experience

chrome/browser/resources/welcome/win10/toggle-screenshot.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.
+
+cr.define('togglescreenshot', function() {
+  'use strict';
+
+  function toggleScreenshots(screenshotImages) {
+    screenshotImages.forEach(function(screenshot) {
+      screenshot.classList.toggle('screenshot-image--visible');
+    });
+  }
+
+  function initialize() {
+    var screenshotImages = document.querySelectorAll('.screenshot-image');
+    sections.forEach(function(section) {
+      var sectionHeading = section.querySelector('.section-heading');
+      sectionHeading.addEventListener('click', function() {
+        toggleScreenshots(screenshotImages);
+      });
+    });
+  }
+
+  return {
+    initialize: initialize
+  };
+});
+
+document.addEventListener('DOMContentLoaded', togglescreenshot.initialize);