--- a/mobile/android/components/BrowserCLH.js
+++ b/mobile/android/components/BrowserCLH.js
@@ -4,17 +4,19 @@
 "use strict";
 
 const {XPCOMUtils} = ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 XPCOMUtils.defineLazyModuleGetters(this, {
   ActorManagerParent: "resource://gre/modules/ActorManagerParent.jsm",
   AppConstants: "resource://gre/modules/AppConstants.jsm",
   DelayedInit: "resource://gre/modules/DelayedInit.jsm",
+  EventDispatcher: "resource://gre/modules/Messaging.jsm",
   GeckoViewUtils: "resource://gre/modules/GeckoViewUtils.jsm",
+  Preferences: "resource://gre/modules/Preferences.jsm",
   Services: "resource://gre/modules/Services.jsm",
 });
 
 function BrowserCLH() {
   this.wrappedJSObject = this;
 }
 
 BrowserCLH.prototype = {
@@ -169,16 +171,42 @@ BrowserCLH.prototype = {
           name: "ActionBarHandler",
           options: {
             capture: true,
             mozSystemGroup: true,
           },
         });
         break;
       }
+
+      case "profile-after-change": {
+        EventDispatcher.instance.registerListener(this, "GeckoView:SetDefaultPrefs");
+        break;
+      }
+    }
+  },
+
+  onEvent(aEvent, aData, aCallback) {
+    switch (aEvent) {
+      case "GeckoView:SetDefaultPrefs": {
+        // While we want to allow setting certain preferences via GeckoView, we
+        // don't want to let it take over completely the management of those
+        // preferences. Therefore we don't handle the "ResetUserPrefs" message,
+        // and consequently we also apply any pref changes directly, i.e. *not*
+        // on the default branch.
+        const prefs = new Preferences();
+        for (const name of Object.keys(aData)) {
+          try {
+            prefs.set(name, aData[name]);
+          } catch (e) {
+            Cu.reportError(`Failed to set preference ${name}: ${e}`);
+          }
+        }
+        break;
+      }
     }
   },
 
   _initLoginManagerEvents: function(aWindow) {
     if (Services.prefs.getBoolPref("reftest.remote", false)) {
       // XXX known incompatibility between reftest harness and form-fill.
       return;
     }

--- a/mobile/android/components/MobileComponents.manifest
+++ b/mobile/android/components/MobileComponents.manifest
@@ -60,16 +60,17 @@ contract @mozilla.org/addons/web-install
 # HelperAppDialog.js
 component {e9d277a0-268a-4ec2-bb8c-10fdf3e44611} HelperAppDialog.js
 contract @mozilla.org/helperapplauncherdialog;1 {e9d277a0-268a-4ec2-bb8c-10fdf3e44611}
 
 # BrowserCLH.js
 component {be623d20-d305-11de-8a39-0800200c9a66} BrowserCLH.js application={aa3c5121-dab2-40e2-81ca-7ea25febc110}
 contract @mozilla.org/browser/browser-clh;1 {be623d20-d305-11de-8a39-0800200c9a66}
 category app-startup BrowserCLH service,@mozilla.org/browser/browser-clh;1
+category profile-after-change BrowserCLH @mozilla.org/browser/browser-clh;1
 
 # ContentDispatchChooser.js
 component {5a072a22-1e66-4100-afc1-07aed8b62fc5} ContentDispatchChooser.js
 contract @mozilla.org/content-dispatch-chooser;1 {5a072a22-1e66-4100-afc1-07aed8b62fc5}
 
 # AddonUpdateService.js
 component {93c8824c-9b87-45ae-bc90-5b82a1e4d877} AddonUpdateService.js
 contract @mozilla.org/browser/addon-update-service;1 {93c8824c-9b87-45ae-bc90-5b82a1e4d877}