- 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
#include "atom/common/native_mate_converters/file_path_converter.h"
#include "atom/common/native_mate_converters/gurl_converter.h"
#include "atom/common/native_mate_converters/image_converter.h"
#include "atom/common/node_includes.h"
#include "atom/common/options_switches.h"
#include "base/command_line.h"
#include "base/environment.h"
#include "base/files/file_path.h"
#include "base/path_service.h"
#include "brightray/browser/brightray_paths.h"
#include "chrome/common/chrome_paths.h"
#include "content/public/browser/client_certificate_delegate.h"
#include "content/public/browser/gpu_data_manager.h"
#include "content/public/browser/render_frame_host.h"
#include "content/public/common/content_switches.h"
#include "native_mate/dictionary.h"
#include "native_mate/object_template_builder.h"
#include "net/ssl/ssl_cert_request_info.h"
#include "ui/base/l10n/l10n_util.h"
#include "ui/gfx/image/image.h"
#if defined(OS_WIN)
#include "base/strings/utf_string_conversions.h"
#include "ui/base/win/shell.h"
#endif
using atom::Browser;
namespace mate {
#if defined(OS_WIN)
template<>
struct Converter<Browser::UserTask> {
  static bool FromV8(v8::Isolate* isolate, v8::Local<v8::Value> val,