Fix an IE bug where the layout engine internally calls the userland `…

…Object.getOwnPropertyNames`.

This is nasty, but since this only occurs when:
a) an iframe is created, in which case, it will be a fresh `window`, so the `cachedWindowNames` should be the same list
b) a user manually grabs the `window` object from a different realm (ie, cross-frame iframe), and passes it into `Object.getOwnPropertyNames`. I'm not sure if this is even possible, but since trying to *do* anything with the property names on the foreign `window` object will throw a security error, I'm OK with not throwing one here.

Fixes #333

es6-shim.js

@@ -1143,9 +1143,19 @@
   if (Object.getOwnPropertyNames) {
     var objectGOPNAcceptsPrimitives = !throwsError(function () { Object.getOwnPropertyNames('foo'); });
     if (!objectGOPNAcceptsPrimitives) {
+      var cachedWindowNames = typeof window === 'object' ? Object.getOwnPropertyNames(window) : [];
       var originalObjectGetOwnPropertyNames = Object.getOwnPropertyNames;
       overrideNative(Object, 'getOwnPropertyNames', function getOwnPropertyNames(value) {
-        return originalObjectGetOwnPropertyNames(ES.ToObject(value));
+        var val = ES.ToObject(value);
+        if (_toString(val) === '[object Window]') {
+          try {
+            return originalObjectGetOwnPropertyNames(val);
+          } catch (e) {
+            // IE bug where layout engine calls userland gOPN for cross-domain `window` objects
+            return _concat([], cachedWindowNames);
+          }
+        }
+        return originalObjectGetOwnPropertyNames(val);
       });
     }
   }

test/object.js

@@ -12,6 +12,7 @@ describe('Object', function () {
 
   var hasSymbols = typeof Symbol === 'function' && typeof Symbol() === 'symbol';
   var ifSymbolsIt = hasSymbols ? it : xit;
+  var ifBrowserIt = typeof window === 'object' && typeof document === 'object' ? it : xit;
 
   if (Object.getOwnPropertyNames) {
     describe('.getOwnPropertyNames()', function () {
@@ -26,6 +27,17 @@ describe('Object', function () {
           expect(Object.getOwnPropertyNames(item)).to.eql(Object.getOwnPropertyNames(Object(item)));
         });
       });
+
+      ifBrowserIt('does not break when an iframe is added', function () {
+        /*global window, document */
+        var div = document.createElement('div');
+        div.innerHTML = '<iframe src="http://xkcd.com"></iframe>';
+        document.body.appendChild(div);
+        setTimeout(function () {
+          document.body.removeChild(div);
+        }, 0);
+        expect(Array.isArray(Object.getOwnPropertyNames(window))).to.eql(true);
+      });
     });
   }