[gjs] promise: Fix ES6 compatibility

[Philip Chimento <pchimento src gnome org>]

commit ee99b27efacd3ac21b3495e572b26707d10bdf9c
Author: Philip Chimento <philip chimento gmail com>
Date:   Mon Jan 16 22:10:53 2017 -0800

    promise: Fix ES6 compatibility
    
    The promises-es6 tests mandate a few checks on the input argument to "new
    Promise()".
    
    https://bugzilla.gnome.org/show_bug.cgi?id=608450

 modules/_lie.js |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/modules/_lie.js b/modules/_lie.js
index 0e69a53..602b52d 100644
--- a/modules/_lie.js
+++ b/modules/_lie.js
@@ -69,9 +69,15 @@ if (!process.browser) {
 // module.exports = Promise;  // removed for GJS
 
 function Promise(resolver) {
+  if (typeof this !== 'object') {
+    throw new TypeError('this must be an object');
+  }
   if (typeof resolver !== 'function') {
     throw new TypeError('resolver must be a function');
   }
+  if (this instanceof Promise && typeof this.state !== 'undefined') {
+    throw new TypeError('this must not be an already-constructed promise');
+  }
   this.state = PENDING;
   this.queue = [];
   this.outcome = void 0;