- 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
const GURL& origin,
                                              bool allowed) {
  if (!allowed)
    return;
  CommonWebContentsDelegate::EnterFullscreenModeForTab(source, origin);
  Emit("enter-html-full-screen");
}
void WebContents::ExitFullscreenModeForTab(content::WebContents* source) {
  CommonWebContentsDelegate::ExitFullscreenModeForTab(source);
  Emit("leave-html-full-screen");
}
void WebContents::RendererUnresponsive(content::WebContents* source) {
  Emit("unresponsive");
  if (type_ == BROWSER_WINDOW)
    owner_window()->RendererUnresponsive(source);
}
void WebContents::RendererResponsive(content::WebContents* source) {
  Emit("responsive");
  if (type_ == BROWSER_WINDOW)
    owner_window()->RendererResponsive(source);
}
bool WebContents::HandleContextMenu(const content::ContextMenuParams& params) {
  if (!params.custom_context.is_pepper_menu)
    return false;
  Emit("pepper-context-menu", std::make_pair(params, web_contents()));
  web_contents()->NotifyContextMenuClosed(params.custom_context);
  return true;
}
bool WebContents::OnGoToEntryOffset(int offset) {