From 3dc926d6daaa23adb23288a3d34ecde169ea2d08 Mon Sep 17 00:00:00 2001
From: Gabor Krizsanits <gkrizsanits@mozilla.com>
Date: Thu, 7 May 2015 14:01:43 +0200
Subject: [PATCH] Bug 1148188 - part1: defaultShims. r=billm

---
 js/xpconnect/src/XPCWrappedNativeScope.cpp    | 11 ++++++-
 .../addoncompat/addoncompat.manifest          |  2 ++
 .../components/addoncompat/defaultShims.js    | 30 +++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 toolkit/components/addoncompat/defaultShims.js

diff --git a/js/xpconnect/src/XPCWrappedNativeScope.cpp b/js/xpconnect/src/XPCWrappedNativeScope.cpp
index 1d31097e0854..a524f1bea4af 100644
--- a/js/xpconnect/src/XPCWrappedNativeScope.cpp
+++ b/js/xpconnect/src/XPCWrappedNativeScope.cpp
@@ -131,10 +131,19 @@ XPCWrappedNativeScope::XPCWrappedNativeScope(JSContext* cx,
 
     JSAddonId* addonId = JS::AddonIdOfObject(aGlobal);
     if (gInterpositionMap) {
+        bool isSystem = nsContentUtils::IsSystemPrincipal(principal);
         if (InterpositionMap::Ptr p = gInterpositionMap->lookup(addonId)) {
-            MOZ_RELEASE_ASSERT(nsContentUtils::IsSystemPrincipal(principal));
+            MOZ_RELEASE_ASSERT(isSystem);
             mInterposition = p->value();
         }
+        // We also want multiprocessCompatible add-ons to have a default interposition.
+        if (!mInterposition && addonId && isSystem) {
+          bool interpositionEnabled = mozilla::Preferences::GetBool(
+            "extensions.interposition.enabled", false);
+          if (interpositionEnabled) {
+            mInterposition = do_GetService("@mozilla.org/addons/default-addon-shims;1");
+          }
+        }
     }
 }
 
diff --git a/toolkit/components/addoncompat/addoncompat.manifest b/toolkit/components/addoncompat/addoncompat.manifest
index 4273bf246c30..4228c8a1a09c 100644
--- a/toolkit/components/addoncompat/addoncompat.manifest
+++ b/toolkit/components/addoncompat/addoncompat.manifest
@@ -1,4 +1,6 @@
 component {1363d5f0-d95e-11e3-9c1a-0800200c9a66} multiprocessShims.js
 contract @mozilla.org/addons/multiprocess-shims;1 {1363d5f0-d95e-11e3-9c1a-0800200c9a66}
+component {50bc93ce-602a-4bef-bf3a-61fc749c4caf} defaultShims.js
+contract @mozilla.org/addons/default-addon-shims;1 {50bc93ce-602a-4bef-bf3a-61fc749c4caf}
 component {dfd07380-6083-11e4-9803-0800200c9a66} remoteTagService.js
 contract @mozilla.org/addons/remote-tag-service;1 {dfd07380-6083-11e4-9803-0800200c9a66}
diff --git a/toolkit/components/addoncompat/defaultShims.js b/toolkit/components/addoncompat/defaultShims.js
new file mode 100644
index 000000000000..8baf29a00a3d
--- /dev/null
+++ b/toolkit/components/addoncompat/defaultShims.js
@@ -0,0 +1,30 @@
+/* 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";
+
+const Cu = Components.utils;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+/**
+ * Using multiprocessShims is optional, and if an add-on is e10s compatible it should not
+ * use it. But in some cases we still want to use the interposition service for various
+ * features so we have a default shim service.
+ */
+
+function DefaultInterpositionService() {
+}
+
+DefaultInterpositionService.prototype = {
+  classID: Components.ID("{50bc93ce-602a-4bef-bf3a-61fc749c4caf}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIAddonInterposition, Ci.nsISupportsWeakReference]),
+
+  interpose: function(addon, target, iid, prop) {
+    return null;
+  },
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([DefaultInterpositionService]);