As described in https://github.com/electron/electron/pull/13769, we had to disable mixed sandbox related tests for Windows CI. We should re-enable them back after finding out the root reason.
atom/app/atom_main_delegate.cc
InitializeFeatureList();
#if defined(OS_MACOSX)
  RegisterAtomCrApp();
#endif
}
content::ContentBrowserClient* AtomMainDelegate::CreateContentBrowserClient() {
  browser_client_.reset(new AtomBrowserClient);
  return browser_client_.get();
}
content::ContentGpuClient* AtomMainDelegate::CreateContentGpuClient() {
  gpu_client_.reset(new AtomGpuClient);
  return gpu_client_.get();
}
content::ContentRendererClient*
AtomMainDelegate::CreateContentRendererClient() {
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          switches::kEnableSandbox) ||
      !base::CommandLine::ForCurrentProcess()->HasSwitch(
          service_manager::switches::kNoSandbox)) {
    renderer_client_.reset(new AtomSandboxedRendererClient);
  } else {
    renderer_client_.reset(new AtomRendererClient);
  }
  return renderer_client_.get();
}
content::ContentUtilityClient* AtomMainDelegate::CreateContentUtilityClient() {