- 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
content::WebContents* source,
      const content::OpenURLParams& params) override;
  void BeforeUnloadFired(content::WebContents* tab,
                         bool proceed,
                         bool* proceed_to_fire_unload) override;
  void MoveContents(content::WebContents* source,
                    const gfx::Rect& pos) override;
  void CloseContents(content::WebContents* source) override;
  void ActivateContents(content::WebContents* contents) override;
  bool IsPopupOrPanel(const content::WebContents* source) const override;
  void HandleKeyboardEvent(
      content::WebContents* source,
      const content::NativeWebKeyboardEvent& event) override;
  void EnterFullscreenModeForTab(content::WebContents* source,
                                 const GURL& origin) override;
  void ExitFullscreenModeForTab(content::WebContents* source) override;
  void RendererUnresponsive(content::WebContents* source) override;
  void RendererResponsive(content::WebContents* source) override;
  bool HandleContextMenu(const content::ContextMenuParams& params) override;
  bool OnGoToEntryOffset(int offset) override;
  void FindReply(content::WebContents* web_contents,
                 int request_id,
                 int number_of_matches,
                 const gfx::Rect& selection_rect,
                 int active_match_ordinal,
                 bool final_update) override;
  bool CheckMediaAccessPermission(
      content::WebContents* web_contents,
      const GURL& security_origin,
      content::MediaStreamType type) override;