Disable non-standard Promise functions in staging

src/js/promise-extra.js

Index: src/js/promise-extra.js
diff --git a/src/js/promise-extra.js b/src/js/promise-extra.js
new file mode 100644
index 0000000000000000000000000000000000000000..2613a500ded843aeb54d134846c0c1618d177beb
--- /dev/null
+++ b/src/js/promise-extra.js
@@ -0,0 +1,30 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+(function(global, utils) {
+
+"use strict";
+
+%CheckIsBootstrapping();
+
+var GlobalPromise = global.Promise;
+
+var PromiseChain = utils.ImportNow("PromiseChain");
+var PromiseDeferred = utils.ImportNow("PromiseDeferred");
+var PromiseResolved = utils.ImportNow("PromiseResolved");
+
+utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [
+  "chain", PromiseChain,
+]);
+
+%InstallToContext([
+  "promise_chain", PromiseChain,
+]);
+
+utils.InstallFunctions(GlobalPromise, DONT_ENUM, [
+  "defer", PromiseDeferred,
+  "accept", PromiseResolved,
+]);
+
+})