- 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
auto command_line = base::CommandLine::ForCurrentProcess();
  if (switch_string == atom::switches::kPpapiFlashPath ||
      switch_string == atom::switches::kClientCertificate ||
      switch_string == switches::kLogNetLog) {
    base::FilePath path;
    args->GetNext(&path);
    command_line->AppendSwitchPath(switch_string, path);
    return;
  }
  std::string value;
  if (args->GetNext(&value))
    command_line->AppendSwitchASCII(switch_string, value);
  else
    command_line->AppendSwitch(switch_string);
}
#if defined(OS_MACOSX)
int DockBounce(const std::string& type) {
  int request_id = -1;
  if (type == "critical")
    request_id = Browser::Get()->DockBounce(Browser::BOUNCE_CRITICAL);
  else if (type == "informational")
    request_id = Browser::Get()->DockBounce(Browser::BOUNCE_INFORMATIONAL);
  return request_id;
}
void DockSetMenu(atom::api::Menu* menu) {
  Browser::Get()->DockSetMenu(menu->model());
}
#endif
void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,