- 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
Emit("activate");
}
bool WebContents::IsPopupOrPanel(const content::WebContents* source) const {
  return type_ == BROWSER_WINDOW;
}
void WebContents::HandleKeyboardEvent(
    content::WebContents* source,
    const content::NativeWebKeyboardEvent& event) {
  if (event.windowsKeyCode == ui::VKEY_ESCAPE && is_html_fullscreen()) {
    
    ExitFullscreenModeForTab(source);
  } else if (type_ == BROWSER_WINDOW) {
    owner_window()->HandleKeyboardEvent(source, event);
  } else if (type_ == WEB_VIEW && guest_delegate_) {
    
    guest_delegate_->HandleKeyboardEvent(source, event);
  }
}
void WebContents::EnterFullscreenModeForTab(content::WebContents* source,
                                            const GURL& origin) {
  auto permission_helper =
      WebContentsPermissionHelper::FromWebContents(source);
  auto callback = base::Bind(&WebContents::OnEnterFullscreenModeForTab,
                             base::Unretained(this), source, origin);
  permission_helper->RequestFullscreenPermission(callback);
}
void WebContents::OnEnterFullscreenModeForTab(content::WebContents* source,