--- a/browser/modules/ReaderParent.jsm
+++ b/browser/modules/ReaderParent.jsm
@@ -21,18 +21,16 @@ const gStringBundle = Services.strings.c
 
 var ReaderParent = {
   _readerModeInfoPanelOpen: false,
 
   MESSAGES: [
     "Reader:ArticleGet",
     "Reader:FaviconRequest",
     "Reader:UpdateReaderButton",
-    "Reader:SetIntPref",
-    "Reader:SetCharPref",
   ],
 
   init: function() {
     let mm = Cc["@mozilla.org/globalmessagemanager;1"].getService(Ci.nsIMessageListenerManager);
     for (let msg of this.MESSAGES) {
       mm.addMessageListener(msg, this);
     }
   },
@@ -71,28 +69,16 @@ var ReaderParent = {
       case "Reader:UpdateReaderButton": {
         let browser = message.target;
         if (message.data && message.data.isArticle !== undefined) {
           browser.isArticle = message.data.isArticle;
         }
         this.updateReaderButton(browser);
         break;
       }
-      case "Reader:SetIntPref": {
-        if (message.data && message.data.name !== undefined) {
-          Services.prefs.setIntPref(message.data.name, message.data.value);
-        }
-        break;
-      }
-      case "Reader:SetCharPref": {
-        if (message.data && message.data.name !== undefined) {
-          Services.prefs.setCharPref(message.data.name, message.data.value);
-        }
-        break;
-      }
     }
   },
 
   updateReaderButton: function(browser) {
     let win = browser.ownerDocument.defaultView;
     if (browser != win.gBrowser.selectedBrowser) {
       return;
     }

--- a/mobile/android/chrome/content/Reader.js
+++ b/mobile/android/chrome/content/Reader.js
@@ -147,28 +147,16 @@ var Reader = {
         break;
 
       case "Reader:UpdateReaderButton": {
         let tab = BrowserApp.getTabForBrowser(message.target);
         tab.browser.isArticle = message.data.isArticle;
         this.updatePageAction(tab);
         break;
       }
-      case "Reader:SetIntPref": {
-        if (message.data && message.data.name !== undefined) {
-          Services.prefs.setIntPref(message.data.name, message.data.value);
-        }
-        break;
-      }
-      case "Reader:SetCharPref": {
-        if (message.data && message.data.name !== undefined) {
-          Services.prefs.setCharPref(message.data.name, message.data.value);
-        }
-        break;
-      }
     }
   },
 
   pageAction: {
     readerModeCallback: function(browser) {
       let url = browser.currentURI.spec;
       if (url.startsWith("about:reader")) {
         let originalURL = ReaderMode.getOriginalUrl(url);

--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -191,18 +191,16 @@ lazilyLoadedObserverScripts.forEach(func
   ["Reader", [
     ["Reader:ArticleGet", false],
     ["Reader:DropdownClosed", true], // 'true' allows us to survive mid-air cycle-collection.
     ["Reader:DropdownOpened", false],
     ["Reader:FaviconRequest", false],
     ["Reader:ToolbarHidden", false],
     ["Reader:SystemUIVisibility", false],
     ["Reader:UpdateReaderButton", false],
-    ["Reader:SetIntPref", false],
-    ["Reader:SetCharPref", false],
   ], "chrome://browser/content/Reader.js"],
 ].forEach(aScript => {
   let [name, messages, script] = aScript;
   XPCOMUtils.defineLazyGetter(window, name, function() {
     let sandbox = {};
     Services.scriptloader.loadSubScript(script, sandbox);
     return sandbox[name];
   });

--- a/toolkit/components/narrate/NarrateControls.jsm
+++ b/toolkit/components/narrate/NarrateControls.jsm
@@ -4,16 +4,17 @@
 
 "use strict";
 
 const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/narrate/VoiceSelect.jsm");
 Cu.import("resource://gre/modules/narrate/Narrator.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/AsyncPrefs.jsm");
 
 this.EXPORTED_SYMBOLS = ["NarrateControls"];
 
 var gStrings = Services.strings.createBundle("chrome://global/locale/narrate.properties");
 
 function NarrateControls(mm, win) {
   this._mm = mm;
   this._winRef = Cu.getWeakReference(win);
@@ -114,26 +115,24 @@ NarrateControls.prototype = {
       case "click":
         this._onButtonClick(evt);
         break;
     }
   },
 
   _onRateInput: function(evt) {
     if (!this._rateMousedown) {
-      this._mm.sendAsyncMessage("Reader:SetIntPref",
-        { name: "narrate.rate", value: evt.target.value });
+      AsyncPrefs.set("narrate.rate", parseInt(evt.target.value, 10));
       this.narrator.setRate(this._convertRate(evt.target.value));
     }
   },
 
   _onVoiceChange: function() {
     let voice = this.voice;
-    this._mm.sendAsyncMessage("Reader:SetCharPref",
-      { name: "narrate.voice", value: voice });
+    AsyncPrefs.set("narrate.voice", voice);
     this.narrator.setVoice(voice);
   },
 
   _onButtonClick: function(evt) {
     switch (evt.target.id) {
       case "narrate-skip-previous":
         this.narrator.skipPrevious();
         break;
@@ -144,17 +143,17 @@ NarrateControls.prototype = {
         if (this.narrator.speaking) {
           this.narrator.stop();
         } else {
           this._updateSpeechControls(true);
           let options = { rate: this.rate, voice: this.voice };
           this.narrator.start(options).then(() => {
             this._updateSpeechControls(false);
           }, err => {
-            Cu.reportError(`Narrate failed: ${err}.`)
+            Cu.reportError(`Narrate failed: ${err}.`);
             this._updateSpeechControls(false);
           });
         }
         break;
       case "narrate-toggle":
         let dropdown = this._doc.getElementById("narrate-dropdown");
         if (dropdown.classList.contains("open")) {
           if (this.narrator.speaking) {

--- a/toolkit/components/reader/AboutReader.jsm
+++ b/toolkit/components/reader/AboutReader.jsm
@@ -7,20 +7,21 @@
 var Ci = Components.interfaces, Cc = Components.classes, Cu = Components.utils;
 
 this.EXPORTED_SYMBOLS = [ "AboutReader" ];
 
 Cu.import("resource://gre/modules/ReaderMode.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
+XPCOMUtils.defineLazyModuleGetter(this, "AsyncPrefs", "resource://gre/modules/AsyncPrefs.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NarrateControls", "resource://gre/modules/narrate/NarrateControls.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Rect", "resource://gre/modules/Geometry.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Task", "resource://gre/modules/Task.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "UITelemetry", "resource://gre/modules/UITelemetry.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "NarrateControls", "resource://gre/modules/narrate/NarrateControls.jsm");
 
 var gStrings = Services.strings.createBundle("chrome://global/locale/aboutReader.properties");
 
 var AboutReader = function(mm, win, articlePromise) {
   let url = this._getOriginalUrl(win);
   if (!(url.startsWith("http://") || url.startsWith("https://"))) {
     let errorMsg = "Only http:// and https:// URLs can be loaded in about:reader.";
     if (Services.prefs.getBoolPref("reader.errors.includeURLs"))
@@ -264,21 +265,17 @@ AboutReader.prototype = {
   _setFontSize: function(newFontSize) {
     let containerClasses = this._doc.getElementById("container").classList;
 
     if (this._fontSize > 0)
       containerClasses.remove("font-size" + this._fontSize);
 
     this._fontSize = newFontSize;
     containerClasses.add("font-size" + this._fontSize);
-
-    this._mm.sendAsyncMessage("Reader:SetIntPref", {
-      name: "reader.font_size",
-      value: this._fontSize
-    });
+    return AsyncPrefs.set("reader.font_size", this._fontSize);
   },
 
   _setupFontSizeButtons: function() {
     const FONT_SIZE_MIN = 1;
     const FONT_SIZE_MAX = 9;
 
     // Sample text shown in Android UI.
     let sampleText = this._doc.getElementById("font-size-sample");
@@ -420,38 +417,32 @@ AboutReader.prototype = {
   },
 
   // Pref values include "dark", "light", and "auto", which automatically switches
   // between light and dark color schemes based on the ambient light level.
   _setColorSchemePref: function(colorSchemePref) {
     this._enableAmbientLighting(colorSchemePref === "auto");
     this._setColorScheme(colorSchemePref);
 
-    this._mm.sendAsyncMessage("Reader:SetCharPref", {
-      name: "reader.color_scheme",
-      value: colorSchemePref
-    });
+    AsyncPrefs.set("reader.color_scheme", colorSchemePref);
   },
 
   _setFontType: function(newFontType) {
     if (this._fontType === newFontType)
       return;
 
     let bodyClasses = this._doc.body.classList;
 
     if (this._fontType)
       bodyClasses.remove(this._fontType);
 
     this._fontType = newFontType;
     bodyClasses.add(this._fontType);
 
-    this._mm.sendAsyncMessage("Reader:SetCharPref", {
-      name: "reader.font_type",
-      value: this._fontType
-    });
+    AsyncPrefs.set("reader.font_type", this._fontType);
   },
 
   _setSystemUIVisibility: function(visible) {
     this._mm.sendAsyncMessage("Reader:SystemUIVisibility", { visible: visible });
   },
 
   _loadArticle: Task.async(function* () {
     let url = this._getOriginalUrl();

--- a/toolkit/modules/AsyncPrefs.jsm
+++ b/toolkit/modules/AsyncPrefs.jsm
@@ -8,19 +8,28 @@ this.EXPORTED_SYMBOLS = ["AsyncPrefs"];
 
 const {interfaces: Ci, utils: Cu, classes: Cc} = Components;
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/Task.jsm");
 
 const kInChildProcess = Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT;
 
 const kAllowedPrefs = new Set([
+  // NB: please leave the testing prefs at the top, and sort the rest alphabetically if you add
+  // anything.
   "testing.allowed-prefs.some-bool-pref",
   "testing.allowed-prefs.some-char-pref",
   "testing.allowed-prefs.some-int-pref",
+
+  "narrate.rate",
+  "narrate.voice",
+
+  "reader.font_size",
+  "reader.font_type",
+  "reader.color_scheme",
 ]);
 
 const kPrefTypeMap = new Map([
   ["boolean", Services.prefs.PREF_BOOL],
   ["number", Services.prefs.PREF_INT],
   ["string", Services.prefs.PREF_STRING],
 ]);