Fix DDC cross-window JS interop on FireFox.

pkg/dev_compiler/tool/input_sdk/lib/js/dart2js/js_dart2js.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Support for interoperating with JavaScript.
  *
  * This library provides access to JavaScript objects from Dart, allowing
  * Dart code to get and set properties, and call methods of JavaScript objects
  * and invoke JavaScript functions. The library takes care of converting
@@ skipping 413 matching lines @@
     var args = <Object>[start, length]..addAll(iterable.skip(skipCount).take(length));
     callMethod('splice', args);
   }
 
   void sort([int compare(E a, E b)]) {
     // Note: arr.sort(null) is a type error in FF
     callMethod('sort', compare == null ? [] : [compare]);
   }
 }
 
+// Cross frame objects should not be considered browser types.
+// We include the the instanceof Object test to filter out cross frame objects
+// on FireFox. Surprisingly on FireFox the instanceof Window test succeeds for
+// cross frame windows while the instanceof Object test fails.
 bool _isBrowserType(o) => JS('bool',
+    '# instanceof Object && ('
     '# instanceof Blob || '
     '# instanceof Event || '
     '(window.KeyRange && # instanceof KeyRange) || '
     '(window.IDBKeyRange && # instanceof IDBKeyRange) || '
     '# instanceof ImageData || '
     '# instanceof Node || '
     // Int8Array.__proto__ is TypedArray.
     '(window.Int8Array && # instanceof Int8Array.__proto__) || '
-    '# instanceof Window', o, o, o, o, o, o, o, o);
+    '# instanceof Window)', o, o, o, o, o, o, o, o, o);
 
 class _DartObject {
   final _dartObj;
   _DartObject(this._dartObj);
 }
 
 dynamic _convertToJS(dynamic o) {
   if (o == null ||
       o is String ||
       o is num ||
@@ skipping 101 matching lines @@
         '  for (let arg of arguments) {'
         '    args.push(arg);'
         '  }'
         '  return #(...args);'
         '}',
         f);
     _interopCaptureThisExpando[f] = ret;
   }
   return ret;
 }