diff --git a/toolkit/components/contentprefs/ContentPrefInstance.jsm b/toolkit/components/contentprefs/ContentPrefInstance.jsm
index dcb9c5f3ec58..59c7e3304593 100644
--- a/toolkit/components/contentprefs/ContentPrefInstance.jsm
+++ b/toolkit/components/contentprefs/ContentPrefInstance.jsm
@@ -71,5 +71,9 @@ ContentPrefInstance.prototype = {
 
   get DBConnection() {
     return this._contentPrefSvc.DBConnection;
+  },
+
+  set loadContext(aLoadContext) {
+    this._context = aLoadContext;
   }
 };
diff --git a/toolkit/components/contentprefs/ContentPrefServiceParent.jsm b/toolkit/components/contentprefs/ContentPrefServiceParent.jsm
index 0866a8b42ee1..02eab2573b10 100644
--- a/toolkit/components/contentprefs/ContentPrefServiceParent.jsm
+++ b/toolkit/components/contentprefs/ContentPrefServiceParent.jsm
@@ -13,6 +13,17 @@ const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/ContentPrefUtils.jsm");
 
+let loadContext = Cc["@mozilla.org/loadcontext;1"].
+                    createInstance(Ci.nsILoadContext);
+let privateLoadContext = Cc["@mozilla.org/privateloadcontext;1"].
+                           createInstance(Ci.nsILoadContext);
+
+function contextArg(context) {
+  return (context && context.usePrivateBrowsing) ?
+           privateLoadContext :
+           loadContext;
+}
+
 var ContentPrefServiceParent = {
   _cps2: null,
 
@@ -96,8 +107,15 @@ var ContentPrefServiceParent = {
 
   receiveMessage(msg) {
     let data = msg.data;
+    let signature;
 
-    if (!_methodsCallableFromChild.some(([method, args]) => method == data.call)) {
+    if (!_methodsCallableFromChild.some(([method, args]) => {
+       if (method == data.call) {
+         signature = args;
+         return true;
+       }
+       return false;
+     })) {
       throw new Error(`Can't call ${data.call} from child!`);
     }
 
@@ -131,6 +149,12 @@ var ContentPrefServiceParent = {
     // Push our special listener.
     args.push(listener);
 
+    // Process context argument for forwarding
+    let contextIndex = signature.indexOf("context");
+    if (contextIndex > -1) {
+      args[contextIndex] = contextArg(args[contextIndex]);
+    }
+
     // And call the function.
     this._cps2[data.call](...args);
   }
diff --git a/toolkit/components/contentprefs/tests/mochitest/test_remoteContentPrefs.html b/toolkit/components/contentprefs/tests/mochitest/test_remoteContentPrefs.html
index 2b95ce0ddd34..826a2ae88009 100644
--- a/toolkit/components/contentprefs/tests/mochitest/test_remoteContentPrefs.html
+++ b/toolkit/components/contentprefs/tests/mochitest/test_remoteContentPrefs.html
@@ -14,6 +14,11 @@
     "use strict";
     /* import-globals-from ../../../../../testing/mochitest/tests/SimpleTest/SpawnTask.js */
 
+    let loadContext = SpecialPowers.Cc["@mozilla.org/loadcontext;1"].
+                        createInstance(SpecialPowers.Ci.nsILoadContext);
+    let privateLoadContext = SpecialPowers.Cc["@mozilla.org/privateloadcontext;1"].
+                        createInstance(SpecialPowers.Ci.nsILoadContext);
+
     SimpleTest.waitForExplicitFinish();
 
     const childFrameURL =
@@ -189,7 +194,9 @@
 
         cps.addObserverForName("test", prefObserver);
 
-        cps.set("http://mochi.test", "test", 42, { usePrivateBrowsing: true });
+        let privateLoadContext = Cc["@mozilla.org/privateloadcontext;1"].
+                            createInstance(Ci.nsILoadContext);
+        cps.set("http://mochi.test", "test", 42, privateLoadContext);
         let event = yield observed.promise;
         tester.is(event.name, "test", "got the right event");
         tester.is(event.isPrivate, true, "the event was for an isPrivate pref");
@@ -265,11 +272,11 @@
                              .getService(SpecialPowers.Ci.nsIContentPrefService2);
       mm.addMessageListener("testRemoteContentPrefs:test2poke", function() {
         info(`received test2poke isPrivate: ${isPrivate}`);
-        cps.setGlobal("testName", 42, {usePrivateBrowsing: isPrivate});
+        cps.setGlobal("testName", 42, isPrivate ? privateLoadContext : loadContext);
       });
       mm.addMessageListener("testRemoteContentPrefs:test2poke2", function() {
         info(`received test2poke2 isPrivate: ${isPrivate}`);
-        cps.removeGlobal("testName", {usePrivateBrowsing: isPrivate});
+        cps.removeGlobal("testName", isPrivate ? privateLoadContext : loadContext);
       });
       mm.sendAsyncMessage("testRemoteContentPrefs:test2", {});
       yield curTest.promise;
diff --git a/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js b/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js
index bf9d59192bdc..eaa1f556ecd3 100644
--- a/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js
+++ b/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js
@@ -131,12 +131,15 @@ var ContentPrefTest = {
 
 };
 
-var gInPrivateBrowsing = false;
-function enterPBMode() {
-  gInPrivateBrowsing = true;
+let loadContext = Cc["@mozilla.org/loadcontext;1"].
+                    createInstance(Ci.nsILoadContext);
+let privateLoadContext = Cc["@mozilla.org/privateloadcontext;1"].
+                           createInstance(Ci.nsILoadContext);
+function enterPBMode(cps) {
+  cps.loadContext = privateLoadContext;
 }
-function exitPBMode() {
-  gInPrivateBrowsing = false;
+function exitPBMode(cps) {
+  cps.loadContext = loadContext;
   Services.obs.notifyObservers(null, "last-pb-context-exited", null);
 }
 
diff --git a/toolkit/components/contentprefs/tests/unit/test_bug248970.js b/toolkit/components/contentprefs/tests/unit/test_bug248970.js
index 5f4aa25c50f6..5b394a51086f 100644
--- a/toolkit/components/contentprefs/tests/unit/test_bug248970.js
+++ b/toolkit/components/contentprefs/tests/unit/test_bug248970.js
@@ -3,8 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 function run_test() {
-    let loadContext = { get usePrivateBrowsing() { return gInPrivateBrowsing; } };
-
     ContentPrefTest.deleteDatabase();
     var cp = new ContentPrefInstance(loadContext);
     do_check_neq(cp, null, "Retrieving the content prefs service failed");
@@ -19,7 +17,7 @@ function run_test() {
       // make sure Zoom-A is retrievable
       do_check_eq(cp.getPref(uri1, pref_name), zoomA);
       // enter private browsing mode
-      enterPBMode();
+      enterPBMode(cp);
       // make sure Zoom-A is retrievable
       do_check_eq(cp.getPref(uri1, pref_name), zoomA);
       // save Zoom-B
@@ -31,7 +29,7 @@ function run_test() {
       // make sure Zoom-A has changed
       do_check_eq(cp.getPref(uri1, pref_name), zoomA_new);
       // exit private browsing mode
-      exitPBMode();
+      exitPBMode(cp);
       // make sure Zoom-A change has not persisted
       do_check_eq(cp.getPref(uri1, pref_name), zoomA);
       // make sure Zoom-B change has not persisted
diff --git a/toolkit/components/contentprefs/tests/unit/test_bug679784.js b/toolkit/components/contentprefs/tests/unit/test_bug679784.js
index 123c8712acb7..477707105d6d 100644
--- a/toolkit/components/contentprefs/tests/unit/test_bug679784.js
+++ b/toolkit/components/contentprefs/tests/unit/test_bug679784.js
@@ -15,8 +15,6 @@ var prefObserver = {
 };
 
 function run_test() {
-  let loadContext = { get usePrivateBrowsing() { return gInPrivateBrowsing; } };
-
   var cps = new ContentPrefInstance(loadContext);
   cps.removeGroupedPrefs();
 
@@ -31,7 +29,7 @@ function run_test() {
   cps.addObserver("value", prefObserver);
   cps.addObserver("value-global", prefObserver);
 
-  enterPBMode();
+  enterPBMode(cps);
 
   // test setPref
   num = prefObserver.setCalledNum;
diff --git a/toolkit/components/contentprefs/tests/unit/test_contentPrefs.js b/toolkit/components/contentprefs/tests/unit/test_contentPrefs.js
index f7e99ea9d16c..6a24e07b6247 100644
--- a/toolkit/components/contentprefs/tests/unit/test_contentPrefs.js
+++ b/toolkit/components/contentprefs/tests/unit/test_contentPrefs.js
@@ -310,8 +310,8 @@ function run_test() {
 
   // Make sure information about private context is properly
   // retrieved by the observer.
-  cps.setPref(uri, "test.observer.private", "test value", {usePrivateBrowsing: true});
-  cps.setPref(uri, "test.observer.normal", "test value", {usePrivateBrowsing: false});
+  cps.setPref(uri, "test.observer.private", "test value", privateLoadContext);
+  cps.setPref(uri, "test.observer.normal", "test value", loadContext);
   cps.removePref(uri, "test.observer.private");
   cps.removePref(uri, "test.observer.normal");
 
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/head.js b/toolkit/components/contentprefs/tests/unit_cps2/head.js
index 07975d9749ff..e24bd017cd82 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/head.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/head.js
@@ -10,6 +10,11 @@ var cps;
 var asyncRunner;
 var next;
 
+let loadContext = Cc["@mozilla.org/loadcontext;1"].
+                    createInstance(Ci.nsILoadContext);
+let privateLoadContext = Cc["@mozilla.org/privateloadcontext;1"].
+                           createInstance(Ci.nsILoadContext);
+
 (function init() {
   // There has to be a profile directory before the CPS service is gotten.
   do_get_profile();
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_getCached.js b/toolkit/components/contentprefs/tests/unit_cps2/test_getCached.js
index 33a965b7f7fb..d6f933655fb6 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_getCached.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_getCached.js
@@ -54,7 +54,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     getCachedOK(["a.com", "foo", context], true, 6);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_getCachedSubdomains.js b/toolkit/components/contentprefs/tests/unit_cps2/test_getCachedSubdomains.js
index 9f2599708fea..873173bfb83a 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_getCachedSubdomains.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_getCachedSubdomains.js
@@ -160,7 +160,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     getCachedSubdomainsOK(["a.com", "foo", context], [["a.com", 6]]);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_getSubdomains.js b/toolkit/components/contentprefs/tests/unit_cps2/test_getSubdomains.js
index d08d6fe695b8..5c71dc408397 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_getSubdomains.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_getSubdomains.js
@@ -45,7 +45,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     yield getSubdomainsOK(["a.com", "foo", context], [["a.com", 6]]);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_observers.js b/toolkit/components/contentprefs/tests/unit_cps2/test_observers.js
index a512cd0c2160..4e254296f897 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_observers.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_observers.js
@@ -9,8 +9,8 @@ function run_test() {
   for (var i = 0; i < tests.length; i++) {
     // Generate two wrappers of each test function that invoke the original test with an
     // appropriate privacy context.
-    var pub = eval("var f = function* " + tests[i].name + "() { yield tests[" + i + "]({ usePrivateBrowsing: false }); }; f");
-    var priv = eval("var f = function* " + tests[i].name + "_private() { yield tests[" + i + "]({ usePrivateBrowsing: true }); }; f");
+    var pub = eval("var f = function* " + tests[i].name + "() { yield tests[" + i + "](privateLoadContext); }; f");
+    var priv = eval("var f = function* " + tests[i].name + "_private() { yield tests[" + i + "](privateLoadContext); }; f");
     allTests.push(pub);
     allTests.push(priv);
   }
@@ -155,7 +155,7 @@ var specialTests = [
   },
 
   function* observerForName_removeAllDomainsSince_private() {
-    let context = {usePrivateBrowsing: true};
+    let context = privateLoadContext;
     yield setWithDate("a.com", "foo", 1, 100, context);
     yield setWithDate("b.com", "foo", 2, 200, context);
     yield setWithDate("c.com", "foo", 3, 300, context);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_remove.js b/toolkit/components/contentprefs/tests/unit_cps2/test_remove.js
index 9853293fc768..05c934e714bf 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_remove.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_remove.js
@@ -147,7 +147,7 @@ var tests = [
     yield set("b.com", "foo", 6);
     yield set("b.com", "bar", 7);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 8, context);
     yield setGlobal("foo", 9, context);
     yield cps.removeByDomainAndName("a.com", "foo", context, makeCallback());
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomains.js b/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomains.js
index 63e1b0552ebe..7683239831aa 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomains.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomains.js
@@ -45,7 +45,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     yield cps.removeAllDomains(context, makeCallback());
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomainsSince.js b/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomainsSince.js
index fa0bf31c37b8..86ba3220dddb 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomainsSince.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_removeAllDomainsSince.js
@@ -62,7 +62,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     yield cps.removeAllDomainsSince(0, context, makeCallback());
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_removeByDomain.js b/toolkit/components/contentprefs/tests/unit_cps2/test_removeByDomain.js
index 1cf6bd8f2e8a..6697ec05bfe6 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_removeByDomain.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_removeByDomain.js
@@ -128,7 +128,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield set("b.com", "foo", 7, context);
     yield setGlobal("foo", 8, context);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_removeByName.js b/toolkit/components/contentprefs/tests/unit_cps2/test_removeByName.js
index fa04656e25ce..237681c2ad4c 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_removeByName.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_removeByName.js
@@ -51,7 +51,7 @@ var tests = [
     yield set("b.com", "foo", 5);
     yield set("b.com", "bar", 6);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 7, context);
     yield setGlobal("foo", 8, context);
     yield set("b.com", "bar", 9, context);
diff --git a/toolkit/components/contentprefs/tests/unit_cps2/test_setGet.js b/toolkit/components/contentprefs/tests/unit_cps2/test_setGet.js
index 546ff0b2bd2b..1a181433f31a 100644
--- a/toolkit/components/contentprefs/tests/unit_cps2/test_setGet.js
+++ b/toolkit/components/contentprefs/tests/unit_cps2/test_setGet.js
@@ -85,7 +85,7 @@ var tests = [
     yield setGlobal("bar", 4);
     yield set("b.com", "foo", 5);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("a.com", "foo", 6, context);
     yield setGlobal("foo", 7, context);
     yield dbOK([
@@ -181,7 +181,7 @@ var tests = [
       {"domain": null, "name": "foo", "value": 4}
     ]);
 
-    let context = { usePrivateBrowsing: true };
+    let context = privateLoadContext;
     yield set("b.com", "foo", 5, context);
 
     yield getOKEx("getByName", ["foo", context], [