- 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
v8::Isolate* isolate, const mate::Dictionary& options) {
  auto handle = mate::CreateHandle(isolate, new WebContents(isolate, options));
  g_wrap_web_contents.Run(handle.ToV8());
  return handle;
}
void ClearWrapWebContents() {
  g_wrap_web_contents.Reset();
}
void SetWrapWebContents(const WrapWebContentsCallback& callback) {
  g_wrap_web_contents = callback;
  
  atom::AtomBrowserMainParts::Get()->RegisterDestructionCallback(
      base::Bind(ClearWrapWebContents));
}
}  
}  
namespace {
void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,
                v8::Local<v8::Context> context, void* priv) {
  v8::Isolate* isolate = context->GetIsolate();
  mate::Dictionary dict(isolate, exports);
  dict.SetMethod("create", &atom::api::WebContents::Create);
  dict.SetMethod("_setWrapWebContents", &atom::api::SetWrapWebContents);
}
}  
NODE_MODULE_CONTEXT_AWARE_BUILTIN(atom_browser_web_contents, Initialize)