- 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
void RequestMediaAccessPermission(
      content::WebContents* web_contents,
      const content::MediaStreamRequest& request,
      const content::MediaResponseCallback& callback) override;
  void RequestToLockMouse(
      content::WebContents* web_contents,
      bool user_gesture,
      bool last_unlocked_by_target) override;
  
  void BeforeUnloadFired(const base::TimeTicks& proceed_time) override;
  void RenderViewDeleted(content::RenderViewHost*) override;
  void RenderProcessGone(base::TerminationStatus status) override;
  void DocumentLoadedInFrame(
      content::RenderFrameHost* render_frame_host) override;
  void DidFinishLoad(content::RenderFrameHost* render_frame_host,
                     const GURL& validated_url) override;
  void DidFailLoad(content::RenderFrameHost* render_frame_host,
                   const GURL& validated_url,
                   int error_code,
                   const base::string16& error_description,
                   bool was_ignored_by_handler) override;
  void DidFailProvisionalLoad(content::RenderFrameHost* render_frame_host,
                              const GURL& validated_url,
                              int error_code,
                              const base::string16& error_description,
                              bool was_ignored_by_handler) override;
  void DidStartLoading() override;
  void DidStopLoading() override;
  void DidGetResourceResponseStart(
      const content::ResourceRequestDetails& details) override;