Reflect.enumerate does not necessarily wait until the first `next()…

…` to determine keys.

Per https://esdiscuss.org/topic/question-about-enumerate-and-property-decision-timing / https://bugs.webkit.org/show_bug.cgi?id=147677

es6-shim.js

@@ -844,8 +844,7 @@
 
   var ObjectIterator = function (object, kind) {
     this.object = object;
-    // Don't generate keys yet.
-    this.array = null;
+    this.array = getAllKeys(object);
     this.kind = kind;
   };
 
@@ -867,11 +866,6 @@
         throw new TypeError('Not an ObjectIterator');
       }
 
-      // Keys not generated
-      if (array === null) {
-        array = this.array = getAllKeys(this.object);
-      }
-
       // Find next key in the object
       while (ES.ToLength(array.length) > 0) {
         key = _shift(array);

test/reflect.js

@@ -315,7 +315,7 @@ describe('Reflect', function () {
     });
 
     describe('keys determined at first next() call', function () {
-      it('does not yield a key added after next()', function () {
+      it('likely does not yield a key added after next()', function () {
         var obj = { a: 1, b: 2 },
         iter = Reflect.enumerate(obj);
 
@@ -326,15 +326,21 @@ describe('Reflect', function () {
         expect(iter.next()).to.deep.equal({ value: undefined, done: true });
       });
 
-      it('yields a key added after enumerate(), before next()', function () {
+      it('may not yield a key added after enumerate(), before next()', function () {
         var obj = { a: 1, b: 2 };
         var iter = Reflect.enumerate(obj);
 
         obj.c = 3;
         expect(iter.next()).to.deep.equal({ value: 'a', done: false });
         expect(iter.next()).to.deep.equal({ value: 'b', done: false });
-        expect(iter.next()).to.deep.equal({ value: 'c', done: false });
-        expect(iter.next()).to.deep.equal({ value: undefined, done: true });
+        var thirdResult = iter.next();
+        // Webkit's implementation of Reflect.enumerate locks the keys at iterator creation
+        if (thirdResult.done) {
+          expect(iter.next()).to.deep.equal({ value: undefined, done: true });
+        } else {
+          expect(iter.next()).to.deep.equal({ value: 'c', done: false });
+          expect(iter.next()).to.deep.equal({ value: undefined, done: true });
+        }
       });
 
       it('does not yield an unyielded key deleted after first next()', function () {