- 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
Emit("did-start-loading");
}
void WebContents::DidStopLoading() {
  Emit("did-stop-loading");
}
void WebContents::DidGetResourceResponseStart(
    const content::ResourceRequestDetails& details) {
  Emit("did-get-response-details",
       details.socket_address.IsEmpty(),
       details.url,
       details.original_url,
       details.http_response_code,
       details.method,
       details.referrer,
       details.headers.get());
}
void WebContents::DidGetRedirectForResourceRequest(
    content::RenderFrameHost* render_frame_host,
    const content::ResourceRedirectDetails& details) {
  Emit("did-get-redirect-request",
       details.url,
       details.new_url,
       (details.resource_type == content::RESOURCE_TYPE_MAIN_FRAME),
       details.http_response_code,
       details.method,
       details.referrer,
       details.headers.get());
}
void WebContents::DidNavigateMainFrame(