- 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/atom_browser_client.cc
#include "content/public/browser/site_instance.h"
#include "content/public/browser/web_contents.h"
#include "content/public/common/web_preferences.h"
#include "net/cert/x509_certificate.h"
#include "net/ssl/ssl_cert_request_info.h"
#include "ppapi/host/ppapi_host.h"
#include "ui/base/l10n/l10n_util.h"
#include "v8/include/v8.h"
namespace atom {
namespace {
bool g_suppress_renderer_process_restart = false;
std::string g_custom_schemes = "";
std::string g_custom_service_worker_schemes = "";
scoped_refptr<net::X509Certificate> ImportCertFromFile(
    const base::FilePath& path) {
  if (path.empty())
    return nullptr;
  std::string cert_data;
  if (!base::ReadFileToString(path, &cert_data))
    return nullptr;
  net::CertificateList certs =
      net::X509Certificate::CreateCertificateListFromBytes(
          cert_data.data(), cert_data.size(),
          net::X509Certificate::FORMAT_AUTO);
  if (certs.empty())
    return nullptr;
  return certs[0];
}
}  
void AtomBrowserClient::SuppressRendererProcessRestartForOnce() {