Add m-esr52 at 52.6.0

1 files changed, 698 insertions, 0 deletions

diff --git a/b2g/chrome/content/settings.js b/b2g/chrome/content/settings.js
new file mode 100644
index 000000000..95921da4c
--- /dev/null
+++ b/b2g/chrome/content/settings.js
@@ -0,0 +1,698 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- /
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+window.performance.mark('gecko-settings-loadstart');
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+var Cr = Components.results;
+
+// The load order is important here SettingsRequestManager _must_ be loaded
+// prior to using SettingsListener otherwise there is a race in acquiring the
+// lock and fulfilling it. If we ever move SettingsListener or this file down in
+// the load order of shell.html things will likely break.
+Cu.import('resource://gre/modules/SettingsRequestManager.jsm');
+Cu.import('resource://gre/modules/XPCOMUtils.jsm');
+Cu.import('resource://gre/modules/Services.jsm');
+Cu.import('resource://gre/modules/AppConstants.jsm');
+
+const isGonk = AppConstants.platform === 'gonk';
+
+if (isGonk) {
+  XPCOMUtils.defineLazyGetter(this, "libcutils", function () {
+    Cu.import("resource://gre/modules/systemlibs.js");
+    return libcutils;
+  });
+}
+
+XPCOMUtils.defineLazyServiceGetter(this, "uuidgen",
+                                   "@mozilla.org/uuid-generator;1",
+                                   "nsIUUIDGenerator");
+
+// Once Bug 731746 - Allow chrome JS object to implement nsIDOMEventTarget
+// is resolved this helper could be removed.
+var SettingsListener = {
+  _callbacks: {},
+
+  init: function sl_init() {
+    if ('mozSettings' in navigator && navigator.mozSettings) {
+      navigator.mozSettings.onsettingchange = this.onchange.bind(this);
+    }
+  },
+
+  onchange: function sl_onchange(evt) {
+    var callback = this._callbacks[evt.settingName];
+    if (callback) {
+      callback(evt.settingValue);
+    }
+  },
+
+  observe: function sl_observe(name, defaultValue, callback) {
+    var settings = window.navigator.mozSettings;
+    if (!settings) {
+      window.setTimeout(function() { callback(defaultValue); });
+      return;
+    }
+
+    if (!callback || typeof callback !== 'function') {
+      throw new Error('Callback is not a function');
+    }
+
+    var req = settings.createLock().get(name);
+    req.addEventListener('success', (function onsuccess() {
+      callback(typeof(req.result[name]) != 'undefined' ?
+        req.result[name] : defaultValue);
+    }));
+
+    this._callbacks[name] = callback;
+  }
+};
+
+SettingsListener.init();
+
+// =================== Mono Audio ======================
+
+SettingsListener.observe('accessibility.monoaudio.enable', false, function(value) {
+  Services.prefs.setBoolPref('accessibility.monoaudio.enable', value);
+});
+
+// =================== Console ======================
+
+SettingsListener.observe('debug.console.enabled', true, function(value) {
+  Services.prefs.setBoolPref('consoleservice.enabled', value);
+  Services.prefs.setBoolPref('layout.css.report_errors', value);
+});
+
+SettingsListener.observe('homescreen.manifestURL', 'Sentinel Value' , function(value) {
+  Services.prefs.setCharPref('dom.mozApps.homescreenURL', value);
+});
+
+// =================== Languages ====================
+SettingsListener.observe('language.current', 'en-US', function(value) {
+  Services.prefs.setCharPref('general.useragent.locale', value);
+
+  let prefName = 'intl.accept_languages';
+  let defaultBranch = Services.prefs.getDefaultBranch(null);
+
+  let intl = '';
+  try {
+    intl = defaultBranch.getComplexValue(prefName,
+                                         Ci.nsIPrefLocalizedString).data;
+  } catch(e) {}
+
+  // Bug 830782 - Homescreen is in English instead of selected locale after
+  // the first run experience.
+  // In order to ensure the current intl value is reflected on the child
+  // process let's always write a user value, even if this one match the
+  // current localized pref value.
+  if (!((new RegExp('^' + value + '[^a-z-_] *[,;]?', 'i')).test(intl))) {
+    value = value + ', ' + intl;
+  } else {
+    value = intl;
+  }
+  Services.prefs.setCharPref(prefName, value);
+
+  if (shell.hasStarted() == false) {
+    shell.bootstrap();
+  }
+});
+
+// =================== RIL ====================
+(function RILSettingsToPrefs() {
+  // DSDS default service IDs
+  ['mms', 'sms', 'telephony'].forEach(function(key) {
+    SettingsListener.observe('ril.' + key + '.defaultServiceId', 0,
+                             function(value) {
+      if (value != null) {
+        Services.prefs.setIntPref('dom.' + key + '.defaultServiceId', value);
+      }
+    });
+  });
+})();
+
+//=================== DeviceInfo ====================
+Components.utils.import('resource://gre/modules/XPCOMUtils.jsm');
+Components.utils.import('resource://gre/modules/ctypes.jsm');
+(function DeviceInfoToSettings() {
+  // MOZ_B2G_VERSION is set in b2g/confvars.sh, and is output as a #define value
+  // from configure.in, defaults to 1.0.0 if this value is not exist.
+  let os_version = AppConstants.MOZ_B2G_VERSION;
+  let os_name = AppConstants.MOZ_B2G_OS_NAME;
+
+  let appInfo = Cc["@mozilla.org/xre/app-info;1"]
+                  .getService(Ci.nsIXULAppInfo);
+
+  // Get the hardware info and firmware revision from device properties.
+  let hardware_info = null;
+  let firmware_revision = null;
+  let product_manufacturer = null;
+  let product_model = null;
+  let product_device = null;
+  let build_number = null;
+  if (isGonk) {
+    hardware_info = libcutils.property_get('ro.hardware');
+    firmware_revision = libcutils.property_get('ro.firmware_revision');
+    product_manufacturer = libcutils.property_get('ro.product.manufacturer');
+    product_model = libcutils.property_get('ro.product.model');
+    product_device = libcutils.property_get('ro.product.device');
+    build_number = libcutils.property_get('ro.build.version.incremental');
+  }
+
+  // Populate deviceinfo settings,
+  // copying any existing deviceinfo.os into deviceinfo.previous_os
+  let lock = window.navigator.mozSettings.createLock();
+  let req = lock.get('deviceinfo.os');
+  req.onsuccess = req.onerror = () => {
+    let previous_os = req.result && req.result['deviceinfo.os'] || '';
+    let software = os_name + ' ' + os_version;
+    let setting = {
+      'deviceinfo.build_number': build_number,
+      'deviceinfo.os': os_version,
+      'deviceinfo.previous_os': previous_os,
+      'deviceinfo.software': software,
+      'deviceinfo.platform_version': appInfo.platformVersion,
+      'deviceinfo.platform_build_id': appInfo.platformBuildID,
+      'deviceinfo.hardware': hardware_info,
+      'deviceinfo.firmware_revision': firmware_revision,
+      'deviceinfo.product_manufacturer': product_manufacturer,
+      'deviceinfo.product_model': product_model,
+      'deviceinfo.product_device': product_device
+    }
+    lock.set(setting);
+  }
+})();
+
+// =================== DevTools ====================
+
+var developerHUD;
+SettingsListener.observe('devtools.overlay', false, (value) => {
+  if (value) {
+    if (!developerHUD) {
+      let scope = {};
+      Services.scriptloader.loadSubScript('chrome://b2g/content/devtools/hud.js', scope);
+      developerHUD = scope.developerHUD;
+    }
+    developerHUD.init();
+  } else {
+    if (developerHUD) {
+      developerHUD.uninit();
+    }
+  }
+});
+
+if (isGonk) {
+  var LogShake;
+  (function() {
+    let scope = {};
+    Cu.import('resource://gre/modules/LogShake.jsm', scope);
+    LogShake = scope.LogShake;
+    LogShake.init();
+  })();
+
+  SettingsListener.observe('devtools.logshake.enabled', false, value => {
+    if (value) {
+      LogShake.enableDeviceMotionListener();
+    } else {
+      LogShake.disableDeviceMotionListener();
+    }
+  });
+
+  SettingsListener.observe('devtools.logshake.qa_enabled', false, value => {
+    if (value) {
+      LogShake.enableQAMode();
+    } else {
+      LogShake.disableQAMode();
+    }
+  });
+}
+
+// =================== Device Storage ====================
+SettingsListener.observe('device.storage.writable.name', 'sdcard', function(value) {
+  if (Services.prefs.getPrefType('device.storage.writable.name') != Ci.nsIPrefBranch.PREF_STRING) {
+    // We clear the pref because it used to be erroneously written as a bool
+    // and we need to clear it before we can change it to have the correct type.
+    Services.prefs.clearUserPref('device.storage.writable.name');
+  }
+  Services.prefs.setCharPref('device.storage.writable.name', value);
+});
+
+// =================== Privacy ====================
+SettingsListener.observe('privacy.donottrackheader.value', 1, function(value) {
+  Services.prefs.setIntPref('privacy.donottrackheader.value', value);
+  // If the user specifically disallows tracking, we set the value of
+  // app.update.custom (update tracking ID) to an empty string.
+  if (value == 1) {
+    Services.prefs.setCharPref('app.update.custom', '');
+    return;
+  }
+  // Otherwise, we assure that the update tracking ID exists.
+  setUpdateTrackingId();
+});
+
+// =================== Crash Reporting ====================
+SettingsListener.observe('app.reportCrashes', 'ask', function(value) {
+  if (value == 'always') {
+    Services.prefs.setBoolPref('app.reportCrashes', true);
+  } else if (value == 'never') {
+    Services.prefs.setBoolPref('app.reportCrashes', false);
+  } else {
+    Services.prefs.clearUserPref('app.reportCrashes');
+  }
+  // This preference is consulted during startup.
+  Services.prefs.savePrefFile(null);
+});
+
+// ================ Updates ================
+/**
+ * For tracking purposes some partners require us to add an UUID to the
+ * update URL. The update tracking ID will be an empty string if the
+ * do-not-track feature specifically disallows tracking and it is reseted
+ * to a different ID if the do-not-track value changes from disallow to allow.
+ */
+function setUpdateTrackingId() {
+  try {
+    let dntEnabled = Services.prefs.getBoolPref('privacy.donottrackheader.enabled');
+    let dntValue =  Services.prefs.getIntPref('privacy.donottrackheader.value');
+    // If the user specifically decides to disallow tracking (1), we just bail out.
+    if (dntEnabled && (dntValue == 1)) {
+      return;
+    }
+
+    let trackingId =
+      Services.prefs.getPrefType('app.update.custom') ==
+      Ci.nsIPrefBranch.PREF_STRING &&
+      Services.prefs.getCharPref('app.update.custom');
+
+    // If there is no previous registered tracking ID, we generate a new one.
+    // This should only happen on first usage or after changing the
+    // do-not-track value from disallow to allow.
+    if (!trackingId) {
+      trackingId = uuidgen.generateUUID().toString().replace(/[{}]/g, "");
+      Services.prefs.setCharPref('app.update.custom', trackingId);
+    }
+  } catch(e) {
+    dump('Error getting tracking ID ' + e + '\n');
+  }
+}
+setUpdateTrackingId();
+
+(function syncUpdatePrefs() {
+  // The update service reads the prefs from the default branch. This is by
+  // design, as explained in bug 302721 comment 43. If we are to successfully
+  // modify them, that's where we need to make our changes.
+  let defaultBranch = Services.prefs.getDefaultBranch(null);
+
+  function syncPrefDefault(prefName) {
+    // The pref value at boot-time will serve as default for the setting.
+    let defaultValue = defaultBranch.getCharPref(prefName);
+    let defaultSetting = {};
+    defaultSetting[prefName] = defaultValue;
+
+    // We back up that value in order to detect pref changes across reboots.
+    // Such a change can happen e.g. when the user installs an OTA update that
+    // changes the update URL format.
+    let backupName = prefName + '.old';
+    try {
+      // Everything relies on the comparison below: When pushing a new Gecko
+      // that changes app.update.url or app.update.channel, we overwrite any
+      // existing setting with the new pref value.
+      let backupValue = Services.prefs.getCharPref(backupName);
+      if (defaultValue !== backupValue) {
+        // If the pref has changed since our last backup, overwrite the setting.
+        navigator.mozSettings.createLock().set(defaultSetting);
+      }
+    } catch(e) {
+      // There was no backup: Overwrite the setting and create a backup below.
+      navigator.mozSettings.createLock().set(defaultSetting);
+    }
+
+    // Initialize or update the backup value.
+    Services.prefs.setCharPref(backupName, defaultValue);
+
+    // Propagate setting changes to the pref.
+    SettingsListener.observe(prefName, defaultValue, value => {
+      if (!value) {
+        // If the setting value is invalid, reset it to its default.
+        navigator.mozSettings.createLock().set(defaultSetting);
+        return;
+      }
+      // Here we will overwrite the pref with the setting value.
+      defaultBranch.setCharPref(prefName, value);
+    });
+  }
+
+  syncPrefDefault('app.update.url');
+  syncPrefDefault('app.update.channel');
+})();
+
+// ================ Debug ================
+(function Composer2DSettingToPref() {
+  //layers.composer.enabled can be enabled in three ways
+  //In order of precedence they are:
+  //
+  //1. mozSettings "layers.composer.enabled"
+  //2. a gecko pref "layers.composer.enabled"
+  //3. presence of ro.display.colorfill at the Gonk level
+
+  var req = navigator.mozSettings.createLock().get('layers.composer2d.enabled');
+  req.onsuccess = function() {
+    if (typeof(req.result['layers.composer2d.enabled']) === 'undefined') {
+      var enabled = false;
+      if (Services.prefs.getPrefType('layers.composer2d.enabled') == Ci.nsIPrefBranch.PREF_BOOL) {
+        enabled = Services.prefs.getBoolPref('layers.composer2d.enabled');
+      } else if (isGonk) {
+        let androidVersion = libcutils.property_get("ro.build.version.sdk");
+        if (androidVersion >= 17 ) {
+          enabled = true;
+        } else {
+          enabled = (libcutils.property_get('ro.display.colorfill') === '1');
+        }
+      }
+      navigator.mozSettings.createLock().set({'layers.composer2d.enabled': enabled });
+    }
+
+    SettingsListener.observe("layers.composer2d.enabled", true, function(value) {
+      Services.prefs.setBoolPref("layers.composer2d.enabled", value);
+    });
+  };
+  req.onerror = function() {
+    dump("Error configuring layers.composer2d.enabled setting");
+  };
+
+})();
+
+// ================ Accessibility ============
+(function setupAccessibility() {
+  let accessibilityScope = {};
+  SettingsListener.observe("accessibility.screenreader", false, function(value) {
+    if (!value) {
+      return;
+    }
+    if (!('AccessFu' in accessibilityScope)) {
+      Cu.import('resource://gre/modules/accessibility/AccessFu.jsm',
+                accessibilityScope);
+      accessibilityScope.AccessFu.attach(window);
+    }
+  });
+})();
+
+// ================ Theming ============
+(function themingSettingsListener() {
+  let themingPrefs = ['ui.menu', 'ui.menutext', 'ui.infobackground', 'ui.infotext',
+                      'ui.window', 'ui.windowtext', 'ui.highlight'];
+
+  themingPrefs.forEach(function(pref) {
+    SettingsListener.observe('gaia.' + pref, null, function(value) {
+      if (value) {
+        Services.prefs.setCharPref(pref, value);
+      }
+    });
+  });
+})();
+
+// =================== Telemetry  ======================
+(function setupTelemetrySettings() {
+  let gaiaSettingName = 'debug.performance_data.shared';
+  let geckoPrefName = 'toolkit.telemetry.enabled';
+  SettingsListener.observe(gaiaSettingName, null, function(value) {
+    if (value !== null) {
+      // Gaia setting has been set; update Gecko pref to that.
+      Services.prefs.setBoolPref(geckoPrefName, value);
+      return;
+    }
+    // Gaia setting has not been set; set the gaia setting to default.
+    let prefValue = AppConstants.MOZ_TELEMETRY_ON_BY_DEFAULT;
+    try {
+      prefValue = Services.prefs.getBoolPref(geckoPrefName);
+    } catch (e) {
+      // Pref not set; use default value.
+    }
+    let setting = {};
+    setting[gaiaSettingName] = prefValue;
+    window.navigator.mozSettings.createLock().set(setting);
+  });
+})();
+
+// =================== Low-precision buffer ======================
+(function setupLowPrecisionSettings() {
+  // The gaia setting layers.low-precision maps to two gecko prefs
+  SettingsListener.observe('layers.low-precision', null, function(value) {
+    if (value !== null) {
+      // Update gecko from the new Gaia setting
+      Services.prefs.setBoolPref('layers.low-precision-buffer', value);
+      Services.prefs.setBoolPref('layers.progressive-paint', value);
+    } else {
+      // Update gaia setting from gecko value
+      try {
+        let prefValue = Services.prefs.getBoolPref('layers.low-precision-buffer');
+        let setting = { 'layers.low-precision': prefValue };
+        window.navigator.mozSettings.createLock().set(setting);
+      } catch (e) {
+        console.log('Unable to read pref layers.low-precision-buffer: ' + e);
+      }
+    }
+  });
+
+  // The gaia setting layers.low-opacity maps to a string gecko pref (0.5/1.0)
+  SettingsListener.observe('layers.low-opacity', null, function(value) {
+    if (value !== null) {
+      // Update gecko from the new Gaia setting
+      Services.prefs.setCharPref('layers.low-precision-opacity', value ? '0.5' : '1.0');
+    } else {
+      // Update gaia setting from gecko value
+      try {
+        let prefValue = Services.prefs.getCharPref('layers.low-precision-opacity');
+        let setting = { 'layers.low-opacity': (prefValue == '0.5') };
+        window.navigator.mozSettings.createLock().set(setting);
+      } catch (e) {
+        console.log('Unable to read pref layers.low-precision-opacity: ' + e);
+      }
+    }
+  });
+})();
+
+// ======================= Dogfooders FOTA ==========================
+if (AppConstants.MOZ_B2G_RIL) {
+  XPCOMUtils.defineLazyModuleGetter(this, "AppsUtils",
+                                    "resource://gre/modules/AppsUtils.jsm");
+
+  SettingsListener.observe('debug.performance_data.dogfooding', false,
+    isDogfooder => {
+      if (!isDogfooder) {
+        dump('AUS:Settings: Not a dogfooder!\n');
+        return;
+      }
+
+      if (!('mozTelephony' in navigator)) {
+        dump('AUS:Settings: There is no mozTelephony!\n');
+        return;
+      }
+
+      if (!('mozMobileConnections' in navigator)) {
+        dump('AUS:Settings: There is no mozMobileConnections!\n');
+        return;
+      }
+
+      let conn = navigator.mozMobileConnections[0];
+      conn.addEventListener('radiostatechange', function onradiostatechange() {
+        if (conn.radioState !== 'enabled') {
+          return;
+        }
+
+        conn.removeEventListener('radiostatechange', onradiostatechange);
+        navigator.mozTelephony.dial('*#06#').then(call => {
+          return call.result.then(res => {
+            if (res.success && res.statusMessage
+                && (res.serviceCode === 'scImei')) {
+              Services.prefs.setCharPref("app.update.imei_hash",
+                                         AppsUtils.computeHash(res.statusMessage, "SHA512"));
+            }
+          });
+        });
+      });
+    });
+}
+
+// =================== Various simple mapping  ======================
+var settingsToObserve = {
+  'accessibility.screenreader_quicknav_modes': {
+    prefName: 'accessibility.accessfu.quicknav_modes',
+    resetToPref: true,
+    defaultValue: ''
+  },
+  'accessibility.screenreader_quicknav_index': {
+    prefName: 'accessibility.accessfu.quicknav_index',
+    resetToPref: true,
+    defaultValue: 0
+  },
+  'app.update.interval': 86400,
+  'apz.overscroll.enabled': true,
+  'browser.safebrowsing.phishing.enabled': true,
+  'browser.safebrowsing.malware.enabled': true,
+  'debug.fps.enabled': {
+    prefName: 'layers.acceleration.draw-fps',
+    defaultValue: false
+  },
+  'debug.log-animations.enabled': {
+    prefName: 'layers.offmainthreadcomposition.log-animations',
+    defaultValue: false
+  },
+  'debug.paint-flashing.enabled': {
+    prefName: 'nglayout.debug.paint_flashing',
+    defaultValue: false
+  },
+  // FIXME: Bug 1185806 - Provide a common device name setting.
+  // Borrow device name from developer's menu to avoid multiple name settings.
+  'devtools.discovery.device': {
+    prefName: 'dom.presentation.device.name',
+    defaultValue: 'Firefox OS'
+  },
+  'devtools.eventlooplag.threshold': 100,
+  'devtools.remote.wifi.visible': {
+    resetToPref: true
+  },
+  'devtools.telemetry.supported_performance_marks': {
+    resetToPref: true
+  },
+
+  'dom.presentation.discovery.enabled': false,
+  'dom.presentation.discoverable': false,
+  'dom.serviceWorkers.testing.enabled': false,
+  'gfx.layerscope.enabled': false,
+  'layers.draw-borders': false,
+  'layers.draw-tile-borders': false,
+  'layers.dump': false,
+  'layers.enable-tiles': AppConstants.platform !== "win",
+  'layers.enable-tiles': true,
+  'layers.effect.invert': false,
+  'layers.effect.grayscale': false,
+  'layers.effect.contrast': '0.0',
+  'layout.display-list.dump': false,
+  'mms.debugging.enabled': false,
+  'network.debugging.enabled': false,
+  'privacy.donottrackheader.enabled': false,
+  'privacy.trackingprotection.enabled': false,
+  'ril.debugging.enabled': false,
+  'ril.radio.disabled': false,
+  'ril.mms.requestReadReport.enabled': {
+    prefName: 'dom.mms.requestReadReport',
+    defaultValue: true
+  },
+  'ril.mms.requestStatusReport.enabled': {
+    prefName: 'dom.mms.requestStatusReport',
+    defaultValue: false
+  },
+  'ril.mms.retrieval_mode': {
+    prefName: 'dom.mms.retrieval_mode',
+    defaultValue: 'manual'
+  },
+  'ril.sms.requestStatusReport.enabled': {
+    prefName: 'dom.sms.requestStatusReport',
+    defaultValue: false
+  },
+  'ril.sms.strict7BitEncoding.enabled': {
+    prefName: 'dom.sms.strict7BitEncoding',
+    defaultValue: false
+  },
+  'ril.sms.maxReadAheadEntries': {
+    prefName: 'dom.sms.maxReadAheadEntries',
+    defaultValue: 7
+  },
+  'services.sync.enabled': {
+    defaultValue: false,
+    notifyChange: true
+  },
+  'ui.touch.radius.leftmm': {
+    resetToPref: true
+  },
+  'ui.touch.radius.topmm': {
+    resetToPref: true
+  },
+  'ui.touch.radius.rightmm': {
+    resetToPref: true
+  },
+  'ui.touch.radius.bottommm': {
+    resetToPref: true
+  },
+  'ui.click_hold_context_menus.delay': {
+    resetToPref: true
+  },
+  'wap.UAProf.tagname': 'x-wap-profile',
+  'wap.UAProf.url': ''
+};
+
+if (AppConstants.MOZ_GRAPHENE) {
+  // Restart required
+  settingsToObserve['layers.async-pan-zoom.enabled'] = false;
+}
+
+function settingObserver(setPref, prefName, setting) {
+  return value => {
+    setPref(prefName, value);
+    if (setting.notifyChange) {
+      SystemAppProxy._sendCustomEvent('mozPrefChromeEvent', {
+        prefName: prefName,
+        value: value
+      });
+    }
+  };
+}
+
+for (let key in settingsToObserve) {
+  let setting = settingsToObserve[key];
+
+  // Allow setting to contain flags redefining prefName and defaultValue.
+  let prefName = setting.prefName || key;
+  let defaultValue = setting.defaultValue;
+  if (defaultValue === undefined) {
+    defaultValue = setting;
+  }
+
+  let prefs = Services.prefs;
+
+  // If requested, reset setting value and defaultValue to the pref value.
+  if (setting.resetToPref) {
+    switch (prefs.getPrefType(prefName)) {
+      case Ci.nsIPrefBranch.PREF_BOOL:
+        defaultValue = prefs.getBoolPref(prefName);
+        break;
+
+      case Ci.nsIPrefBranch.PREF_INT:
+        defaultValue = prefs.getIntPref(prefName);
+        break;
+
+      case Ci.nsIPrefBranch.PREF_STRING:
+        defaultValue = prefs.getCharPref(prefName);
+        break;
+    }
+
+    let setting = {};
+    setting[key] = defaultValue;
+    window.navigator.mozSettings.createLock().set(setting);
+  }
+
+  // Figure out the right setter function for this type of pref.
+  let setPref;
+  switch (typeof defaultValue) {
+    case 'boolean':
+      setPref = prefs.setBoolPref.bind(prefs);
+      break;
+
+    case 'number':
+      setPref = prefs.setIntPref.bind(prefs);
+      break;
+
+    case 'string':
+      setPref = prefs.setCharPref.bind(prefs);
+      break;
+  }
+
+  SettingsListener.observe(key, defaultValue,
+                           settingObserver(setPref, prefName, setting));
+};