* 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
ChildProcessLaunched(content::PROCESS_TYPE_RENDERER,
                       host->GetProcess().Handle());
  
  
  
  content::WebContents* web_contents =
      AtomBrowserClient::Get()->GetWebContentsFromProcessID(host->GetID());
  if (web_contents)
    WebContents::FromOrCreate(v8::Isolate::GetCurrent(), web_contents);
}
void App::RenderProcessDisconnected(base::ProcessId host_pid) {
  ChildProcessDisconnected(host_pid);
}
void App::ChildProcessLaunched(int process_type, base::ProcessHandle handle) {
  auto pid = base::GetProcId(handle);
#if defined(OS_MACOSX)
  std::unique_ptr<base::ProcessMetrics> metrics(
      base::ProcessMetrics::CreateProcessMetrics(
          handle, content::BrowserChildProcessHost::GetPortProvider()));
#else
  std::unique_ptr<base::ProcessMetrics> metrics(
      base::ProcessMetrics::CreateProcessMetrics(handle));
#endif
  app_metrics_[pid] = std::make_unique<atom::ProcessMetric>(process_type, pid,
                                                            std::move(metrics));
}
void App::ChildProcessDisconnected(base::ProcessId pid) {