* Electron version: 1.6.10
* Operating system: macOS Sierra 10.12.4 (16E195)

# Improve Handoff API support

Hi!

Today the API of Handoff provides the methods: `setUserActivity`, `getCurrentActivityType` and dispatch the event `continue-activity`

I'm using Handoff and noticed that in some circumstances the broadcast takes a long time to update its userInfo which does not happen on the native iOS client

1. To invalidate or resign the current activity we currently need to create a non-existing activity type and set it as the current activity. There's no way to handle the activity life cycle through electron.
2. When we need to update a given user activity userInfo frequently (i.e in response to a search bar's text changes), we have no efficient way. Setting a new userActivity with the updated information takes several seconds to bridge, whereas doing this on iOS native app is instantaneous.

I believe that exposing a bit more of the NSUserActivity API to Electron would help, namely `becomeCurrent`, `resignCurrent` and `invalidate` which would address point 1, and `needsSave` and a new event to allow updating an activity when needed to address point 2.
These are described in more detail in https://developer.apple.com/reference/foundation/nsuseractivity.

I'm are open to help in any way i can such as explaining how the native API work, providing sample code or testing possible implementations

Thank you!
atom/browser/api/atom_api_app.cc
Browser::LoginItemSettings options;
  args->GetNext(&options);
  return Browser::Get()->GetLoginItemSettings(options);
}
#if defined(USE_NSS_CERTS)
void App::ImportCertificate(const base::DictionaryValue& options,
                            net::CompletionRepeatingCallback callback) {
  auto browser_context = AtomBrowserContext::From("", false);
  if (!certificate_manager_model_) {
    auto copy = base::DictionaryValue::From(
        base::Value::ToUniquePtrValue(options.Clone()));
    CertificateManagerModel::Create(
        browser_context.get(),
        base::BindRepeating(&App::OnCertificateManagerModelCreated,
                            base::Unretained(this), base::Passed(&copy),
                            callback));
    return;
  }
  int rv = ImportIntoCertStore(certificate_manager_model_.get(), options);
  std::move(callback).Run(rv);
}
void App::OnCertificateManagerModelCreated(