Create chrome://device-emulator and add the ability to get a battery percentage and send an updated…

chrome/browser/resources/chromeos/emulator/device_emulator.js

+// Copyright 2015 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('device_emulator', function() {
+  'use strict';
+
+  /**
+   * Updates the UI with the battery status

[michaelpg, 2015/06/25 18:18:19]

nit: end comments/sentences with a period

[rfrappier, 2015/06/25 21:43:24]

Done.

+   * @param {number} percent Battery percentage (out of 100).
+   */
+  function setBatteryInfo(percent) {
+    var slider = $('battery-percent-slider');
+    var text = $('battery-percent-text');
+
+    slider.value = percent;
+    text.value = percent.toString();
+  }
+
+  /**
+   * Event listener fired when the battery percent slider is moved and the mouse
+   * is released. Updates the ChromeOS UI.
+   * @param {event} event Contains information about the event which was fired.

[michaelpg, 2015/06/25 18:18:19]

{Event}

[rfrappier, 2015/06/25 21:43:24]

Done.

+   */
+  function onBatterySliderChange(event) {
+    var slider = event.target;
+    chrome.send('updateBatteryInfo', [slider.valueAsNumer]);
+  }
+
+  /**
+   * Event listener fired when the battery percent slider is moved. Updates
+   * the battery slider's associated text input.
+   * @param {event} event Contains information about the event which was fired.
+   */
+  function onBatterySliderInput(event) {
+    var slider = event.target;
+    var text = $('battery-percent-text');
+
+    text.value = slider.value;
+  }
+
+  /**
+   * Event listener fired when a percentage is entered in the battery
+   * percentage text input. Updates the slider and ChromeOS UI.
+   * @param {event} event Contains information about the event which was fired.
+   */
+  function onBatteryTextChange(event) {
+    var text = event.target;
+    var slider = $('battery-percent-slider');
+    var percent = text.valueAsNumber;
+
+    if (isNaN(percent)) {
+      percent = 0;
+      text.valueAsNumber = 0;
+    }
+
+    slider.value = percent;
+
+    chrome.send('updateBatteryInfo', [percent]);
+  }
+
+  function initialize() {
+    chrome.send('requestBatteryInfo');
+
+    var slider = $('battery-percent-slider');
+    var text = $('battery-percent-text');
+
+    slider.addEventListener('change', onBatterySliderChange);
+    slider.addEventListener('input', onBatterySliderInput);
+    text.addEventListener('input', onBatteryTextChange);
+  }
+
+  // Return an object with all of the exports.
+  return {
+    initialize: initialize,
+    setBatteryInfo: setBatteryInfo,
+  };
+});
+
+document.addEventListener('DOMContentLoaded', device_emulator.initialize);