* 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
char temporaryCString[kCStringSize] = {0};
  CFStringGetCString(value, temporaryCString, kCStringSize,
                     kCFStringEncodingUTF8);
  region = temporaryCString;
#else
  const char* locale_ptr = setlocale(LC_TIME, NULL);
  if (!locale_ptr)
    locale_ptr = setlocale(LC_NUMERIC, NULL);
  if (locale_ptr) {
    std::string locale = locale_ptr;
    std::string::size_type rpos = locale.find('.');
    if (rpos != std::string::npos)
      locale = locale.substr(0, rpos);
    rpos = locale.find('_');
    if (rpos != std::string::npos && rpos + 1 < locale.size())
      region = locale.substr(rpos + 1);
  }
#endif
  return region.size() == 2 ? region : std::string();
}
void App::OnSecondInstance(const base::CommandLine::StringVector& cmd,
                           const base::FilePath& cwd) {
  Emit("second-instance", cmd, cwd);
}
bool App::HasSingleInstanceLock() const {
  if (process_singleton_)
    return true;
  return false;
}
bool App::RequestSingleInstanceLock() {