--- a/dom/activities/ActivityRequestHandler.js
+++ b/dom/activities/ActivityRequestHandler.js
@@ -31,37 +31,34 @@ function ActivityRequestHandler() {
   // ActivityRequestHandler object.
 }
 
 ActivityRequestHandler.prototype = {
   init: function arh_init(aWindow) {
     this._window = aWindow;
   },
 
-  __init: function arh___init(aId, aOptions, aReturnValue) {
+  __init: function arh___init(aId, aOptions) {
     this._id = aId;
     this._options = aOptions;
-    this._returnValue = aReturnValue;
   },
 
   get source() {
     // We need to clone this object because the this._options.data has
     // the type any in WebIDL which will cause the binding layer to pass
     // the value which is a COW unmodified to content.
     return Cu.cloneInto(this._options, this._window);
   },
 
   postResult: function arh_postResult(aResult) {
-    if (this._returnValue) {
-      cpmm.sendAsyncMessage("Activity:PostResult", {
-        "id": this._id,
-        "result": aResult
-      });
-      Services.obs.notifyObservers(null, "activity-success", this._id);
-    }
+    cpmm.sendAsyncMessage("Activity:PostResult", {
+      "id": this._id,
+      "result": aResult
+    });
+    Services.obs.notifyObservers(null, "activity-success", this._id);
   },
 
   postError: function arh_postError(aError) {
     cpmm.sendAsyncMessage("Activity:PostError", {
       "id": this._id,
       "error": aError
     });
     Services.obs.notifyObservers(null, "activity-error", this._id);

--- a/dom/activities/ActivityWrapper.js
+++ b/dom/activities/ActivityWrapper.js
@@ -32,20 +32,17 @@ ActivityWrapper.prototype = {
     debug("Wrapping " + JSON.stringify(aMessage));
 
     // This message is useful to communicate that the activity message has been
     // properly received by the app. If the app will be killed, the
     // ActivitiesService will be able to fire an error and complete the
     // Activity workflow.
     cpmm.sendAsyncMessage("Activity:Ready", { id: aMessage.id });
 
-    // Gecko should ignore |postResult| calls for WebActivities with no returnValue
-    // We need to pass returnValue to ActivityRequestHandler constructor to then properly
-    // decide if should call postResult or not
-    let handler = new aWindow.ActivityRequestHandler(aMessage.id, aMessage.payload, aMessage.target.returnValue);
+    let handler = new aWindow.ActivityRequestHandler(aMessage.id, aMessage.payload);
 
     // When the activity window is closed, fire an error to notify the activity
     // caller of the situation.
     // We don't need to check whether the activity itself already sent
     // back something since ActivitiesService.jsm takes care of that.
     let util = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                       .getInterface(Ci.nsIDOMWindowUtils);
     let innerWindowID = util.currentInnerWindowID;

--- a/dom/webidl/ActivityRequestHandler.webidl
+++ b/dom/webidl/ActivityRequestHandler.webidl
@@ -1,15 +1,15 @@
 /* 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/. */
 
 [Pref="dom.sysmsg.enabled",
  JSImplementation="@mozilla.org/dom/activities/request-handler;1",
- ChromeConstructor(DOMString id, optional ActivityOptions options, optional boolean returnvalue),
+ ChromeConstructor(DOMString id, optional ActivityOptions options),
  ChromeOnly]
 interface ActivityRequestHandler
 {
     [UnsafeInPrerendering]
     void postResult(any result);
     [UnsafeInPrerendering]
     void postError(DOMString error);
     [Pure, Cached, Frozen]