chromeos: Add Power device page to chrome://md-settings.

chrome/browser/resources/settings/device_page/power.js

+// Copyright 2017 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.
+
+/**
+ * @fileoverview
+ * 'settings-power' is the settings subpage for power settings.
+ */
+Polymer({
+  is: 'settings-power',
+
+  behaviors: [
+    I18nBehavior,
+    WebUIListenerBehavior,
+  ],
+
+  properties: {
+    enablePowerSettings: Boolean,

[michaelpg, 2017/03/01 05:20:39]

if this is false, we probably should bail out in ready() as this UI would be
unusable (see navigateToPreviousRoute())

[Daniel Erat, 2017/03/01 23:01:53]

done (i think; let me know if i got it wrong)

+
+    /** @private {string} ID of the selected power source, or ''. */
+    selectedPowerSourceId_: String,
+
+    /** @private {!settings.BatteryStatus|undefined} */
+    batteryStatus_: Object,
+
+    /** @private {boolean} Whether a low-power (USB) charger is being used. */
+    lowPowerCharger_: Boolean,
+
+    /**
+     * List of available dual-role power sources, if enablePowerSettings_ is on.

[michaelpg, 2017/03/01 05:20:39]

enablePowerSettings (no underscore)

[Daniel Erat, 2017/03/01 23:01:53]

Done.

+     * @private {!Array<!settings.PowerSource>|undefined}
+     */
+    powerSources_: Array,
+
+    /** @private */
+    powerSourceLabel_: {
+      type: String,
+      computed:
+          'computePowerSourceLabel_(powerSources_, batteryStatus_.calculating)',
+    },
+
+    /** @private */
+    showPowerSourceDropdown_: {
+      type: Boolean,
+      computed: 'computeShowPowerSourceDropdown_(powerSources_)',
+      value: false,
+    },
+
+    /**
+     * The name of the dedicated charging device being used, if present.
+     * @private {string}
+     */
+    powerSourceName_: {
+      type: String,
+      computed: 'computePowerSourceName_(powerSources_, lowPowerCharger_)',
+    },
+  },
+
+  /** @override */
+  attached: function() {
+    if (this.enablePowerSettings) {

[stevenjb, 2017/03/01 17:19:43]

In practice this is fine since enablePowerSettings comes from loadTimeData which
will always be set before this is attached. However since this is provided by
device-page it would be nice to add a comment here that enablePowerSettings
comes from loadTimeData. (Alternately this could be moved to an
enablePowerSettings listener).
Also: invert and early exit and, as Michael suggests, close the subpage if
!enablePowerSettings (or do that in ready() which gets called first:
https://www.polymer-project.org/1.0/docs/devguide/registering-elements).

[Daniel Erat, 2017/03/01 23:01:53]

Done.

+      this.addWebUIListener(
+          'battery-status-changed', this.set.bind(this, 'batteryStatus_'));
+      this.addWebUIListener(
+          'power-sources-changed', this.powerSourcesChanged_.bind(this));
+      settings.DevicePageBrowserProxyImpl.getInstance().updatePowerStatus();
+    }
+  },
+
+  /**
+   * @param {!Array<!settings.PowerSource>|undefined} powerSources
+   * @param {boolean} calculating
+   * @return {string} The primary label for the power source row.
+   * @private
+   */
+  computePowerSourceLabel_: function(powerSources, calculating) {
+    return this.i18n(
+        calculating ?
+            'calculatingPower' :
+            powerSources.length ? 'powerSourceLabel' : 'powerSourceBattery');
+  },
+
+  /**
+   * @param {!Array<!settings.PowerSource>} powerSources
+   * @return {boolean} True if at least one power source is attached and all of
+   *     them are dual-role (no dedicated chargers).
+   * @private
+   */
+  computeShowPowerSourceDropdown_: function(powerSources) {
+    return powerSources.length > 0 && powerSources.every(function(source) {
+      return source.type == settings.PowerDeviceType.DUAL_ROLE_USB;
+    });
+  },
+
+  /**
+   * @param {!Array<!settings.PowerSource>} powerSources
+   * @param {boolean} lowPowerCharger
+   * @return {string} Description of the power source.
+   * @private
+   */
+  computePowerSourceName_: function(powerSources, lowPowerCharger) {
+    if (lowPowerCharger)
+      return this.i18n('powerSourceLowPowerCharger');
+    if (powerSources.length)
+      return this.i18n('powerSourceAcAdapter');
+    return '';
+  },
+
+  onPowerSourceChange_: function() {
+    settings.DevicePageBrowserProxyImpl.getInstance().setPowerSource(
+        this.$$('#powerSource').value);
+  },
+
+  /**
+   * @param {!Array<settings.PowerSource>} sources External power sources.
+   * @param {string} selectedId The ID of the currently used power source.
+   * @param {boolean} lowPowerCharger Whether the currently used power source
+   *     is a low-powered USB charger.
+   * @private
+   */
+  powerSourcesChanged_: function(sources, selectedId, lowPowerCharger) {
+    this.powerSources_ = sources;
+    this.selectedPowerSourceId_ = selectedId;
+    this.lowPowerCharger_ = lowPowerCharger;
+  },
+
+  /**
+   * @param {*} lhs
+   * @param {*} rhs
+   * @return {boolean}
+   * @private
+   */
+  isEqual_: function(lhs, rhs) {
+    return lhs === rhs;
+  },
+});