- Electron version: v0.36.9
- Operating system: Windows 10/OS X

In #779 a `disposition` was added to the `new-window` event in [webContents](https://github.com/atom/electron/blob/master/docs/api/web-contents.md#event-new-window) but it always seems to be set to `new-window` when clicking on target="_blank" links in our web app wrapper: https://github.com/irccloud/irccloud-desktop/blob/v0.1.3/app/main.js#L109

If I Ctrl (Win) or Cmd (OS X) or middle click on links, I would expect to see a `background-tab` disposition, as in Chrome that will open links in a background tab, while keeping focus on the current tab. I'd like to catch this behaviour to set `activate` to false in `shell.openExternal`.

Is this possible?

atom/browser/api/atom_api_web_contents.cc
PrintSettings* out) {
    mate::Dictionary dict;
    if (!ConvertFromV8(isolate, val, &dict))
      return false;
    dict.Get("silent", &(out->silent));
    dict.Get("printBackground", &(out->print_background));
    return true;
  }
};
template<>
struct Converter<WindowOpenDisposition> {
  static v8::Local<v8::Value> ToV8(v8::Isolate* isolate,
                                   WindowOpenDisposition val) {
    std::string disposition = "other";
    switch (val) {
      case CURRENT_TAB: disposition = "default"; break;
      case NEW_FOREGROUND_TAB: disposition = "foreground-tab"; break;
      case NEW_BACKGROUND_TAB: disposition = "background-tab"; break;
      case NEW_POPUP: case NEW_WINDOW: disposition = "new-window"; break;
      default: break;
    }
    return mate::ConvertToV8(isolate, disposition);
  }
};
template<>
struct Converter<net::HttpResponseHeaders*> {
  static v8::Local<v8::Value> ToV8(v8::Isolate* isolate,