- 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
if (IsDevToolsOpened())
    CloseDevTools();
  else
    OpenDevTools(nullptr);
}
void WebContents::InspectElement(int x, int y) {
  if (type_ == REMOTE)
    return;
  OpenDevTools(nullptr);
  scoped_refptr<content::DevToolsAgentHost> agent(
    content::DevToolsAgentHost::GetOrCreateFor(web_contents()));
  agent->InspectElement(x, y);
}
void WebContents::InspectServiceWorker() {
  if (type_ == REMOTE)
    return;
  for (const auto& agent_host : content::DevToolsAgentHost::GetOrCreateAll()) {
    if (agent_host->GetType() ==
        content::DevToolsAgentHost::TYPE_SERVICE_WORKER) {
      OpenDevTools(nullptr);
      managed_web_contents()->AttachTo(agent_host);
      break;
    }
  }
}
void WebContents::HasServiceWorker(