- 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.h
namespace api {
class WebContents : public mate::TrackableObject<WebContents>,
                    public CommonWebContentsDelegate,
                    public content::WebContentsObserver {
 public:
  
  using PrintToPDFCallback =
      base::Callback<void(v8::Local<v8::Value>, v8::Local<v8::Value>)>;
  
  static mate::Handle<WebContents> CreateFrom(
      v8::Isolate* isolate, content::WebContents* web_contents);
  
  static mate::Handle<WebContents> Create(
      v8::Isolate* isolate, const mate::Dictionary& options);
  int GetID() const;
  bool Equal(const WebContents* web_contents) const;
  void LoadURL(const GURL& url, const mate::Dictionary& options);
  void DownloadURL(const GURL& url);
  GURL GetURL() const;
  base::string16 GetTitle() const;
  bool IsLoading() const;
  bool IsWaitingForResponse() const;
  void Stop();
  void ReloadIgnoringCache();
  void GoBack();
  void GoForward();
  void GoToOffset(int offset);
  bool IsCrashed() const;
  void SetUserAgent(const std::string& user_agent);
  std::string GetUserAgent();