- 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
PrintSettings settings = { false, false };
  if (args->Length() == 1 && !args->GetNext(&settings)) {
    args->ThrowError();
    return;
  }
  printing::PrintViewManagerBasic::FromWebContents(web_contents())->
      PrintNow(settings.silent, settings.print_background);
}
void WebContents::PrintToPDF(const base::DictionaryValue& setting,
                             const PrintToPDFCallback& callback) {
  printing::PrintPreviewMessageHandler::FromWebContents(web_contents())->
      PrintToPDF(setting, callback);
}
void WebContents::AddWorkSpace(mate::Arguments* args,
                               const base::FilePath& path) {
  if (path.empty()) {
    args->ThrowError("path cannot be empty");
    return;
  }
  DevToolsAddFileSystem(path);
}
void WebContents::RemoveWorkSpace(mate::Arguments* args,
                                  const base::FilePath& path) {
  if (path.empty()) {
    args->ThrowError("path cannot be empty");
    return;
  }
  DevToolsRemoveFileSystem(path);
}
void WebContents::Undo() {