{"action":"created","issue":{"url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/648","labels_url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/648/labels{/name}","comments_url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/648/comments","events_url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/648/events","html_url":"https://github.com/dart-lang/polymer-dart/issues/648","id":118194339,"number":648,"title":"\"Requesting mirror on un-marked class, superclass of 'JsProxy'\" in Firefox","user":{"login":"zoechi","id":405837,"avatar_url":"https://avatars.githubusercontent.com/u/405837?v=3","gravatar_id":"","url":"https://api.github.com/users/zoechi","html_url":"https://github.com/zoechi","followers_url":"https://api.github.com/users/zoechi/followers","following_url":"https://api.github.com/users/zoechi/following{/other_user}","gists_url":"https://api.github.com/users/zoechi/gists{/gist_id}","starred_url":"https://api.github.com/users/zoechi/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/zoechi/subscriptions","organizations_url":"https://api.github.com/users/zoechi/orgs","repos_url":"https://api.github.com/users/zoechi/repos","events_url":"https://api.github.com/users/zoechi/events{/privacy}","received_events_url":"https://api.github.com/users/zoechi/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":5,"created_at":"2015-11-21T12:54:33Z","updated_at":"2015-11-24T13:34:03Z","closed_at":null,"body":"```dart\r\n  @property List columnCheckboxes = [];\r\n\r\n  ...\r\n  void _handleHeaderContextMenu(HeaderContextMenu e) {\r\n    for (int i = 0; i < _columns.length; i++) {\r\n      CbData cb = new CbData(_columns[i].id);\r\n\r\n      cb.checked = _grid.getColumnIndex(_columns[i].id) != null;\r\n      cb.text = _columns[i].name;\r\n      add('columnCheckboxes', cb); // <= fails\r\n    }\r\n  }\r\n\r\nI wasn't able to get a Dart stack trace from Firefox (using source maps)\r\nHope this helps a bit:\r\n\r\n![image](https://cloud.githubusercontent.com/assets/405837/11318511/87af4fa2-9055-11e5-89d8-70c69392ed97.png)\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/comments/159268760","html_url":"https://github.com/dart-lang/polymer-dart/issues/648#issuecomment-159268760","issue_url":"https://api.github.com/repos/dart-lang/polymer-dart/issues/648","id":159268760,"user":{"login":"zoechi","id":405837,"avatar_url":"https://avatars.githubusercontent.com/u/405837?v=3","gravatar_id":"","url":"https://api.github.com/users/zoechi","html_url":"https://github.com/zoechi","followers_url":"https://api.github.com/users/zoechi/followers","following_url":"https://api.github.com/users/zoechi/following{/other_user}","gists_url":"https://api.github.com/users/zoechi/gists{/gist_id}","starred_url":"https://api.github.com/users/zoechi/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/zoechi/subscriptions","organizations_url":"https://api.github.com/users/zoechi/orgs","repos_url":"https://api.github.com/users/zoechi/repos","events_url":"https://api.github.com/users/zoechi/events{/privacy}","received_events_url":"https://api.github.com/users/zoechi/received_events","type":"User","site_admin":false},"created_at":"2015-11-24T13:34:03Z","updated_at":"2015-11-24T13:34:03Z","body":"I just tried again.\r\nCurrenty I get the error \"element is not subclass of TemplateElement\" in Firefox. \r\nIs this also what you were seeing @jakemac53 ?"}}