diff -r 000000000000 -r 6474c204b198 dom/apps/src/InterAppComm.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/apps/src/InterAppComm.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,26 @@
+/* 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/. */
+
+#include "InterAppComm.h"
+#include "nsContentUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsJSPrincipals.h"
+#include "mozilla/Preferences.h"
+#include "AccessCheck.h"
+
+using namespace mozilla::dom;
+
+/* static */ bool
+InterAppComm::EnabledForScope(JSContext* /* unused */,
+			      JS::Handle<JSObject*> /* unused */)
+{
+  // Disable the constructors if they're disabled by the preference for sure.
+  if (!Preferences::GetBool("dom.inter-app-communication-api.enabled", false)) {
+  	return false;
+  }
+
+  // Only expose the constructors to the chrome codes for Gecko internal uses.
+  // The content pages shouldn't be aware of the constructors.
+  return nsContentUtils::ThreadsafeIsCallerChrome();
+}