- 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_app.cc
v8::Isolate* isolate,
    std::shared_ptr<content::ClientCertificateDelegate> delegate,
    mate::Arguments* args) {
  mate::Dictionary cert_data;
  if (!args->GetNext(&cert_data)) {
    args->ThrowError();
    return;
  }
  v8::Local<v8::Object> data;
  if (!cert_data.Get("data", &data))
    return;
  auto certs = net::X509Certificate::CreateCertificateListFromBytes(
      node::Buffer::Data(data), node::Buffer::Length(data),
      net::X509Certificate::FORMAT_AUTO);
  if (certs.size() > 0)
    delegate->ContinueWithCertificate(certs[0].get());
}
void PassLoginInformation(scoped_refptr<LoginHandler> login_handler,
                          mate::Arguments* args) {
  base::string16 username, password;
  if (args->GetNext(&username) && args->GetNext(&password))
    login_handler->Login(username, password);
  else
    login_handler->CancelAuth();
}
}  
App::App() {