* 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
AtomBrowserClient::Get()->SetUserAgent(user_agent);
}
std::string App::GetUserAgentFallback() {
  return AtomBrowserClient::Get()->GetUserAgent();
}
void App::SetBrowserClientCanUseCustomSiteInstance(bool should_disable) {
  AtomBrowserClient::Get()->SetCanUseCustomSiteInstance(should_disable);
}
bool App::CanBrowserClientUseCustomSiteInstance() {
  return AtomBrowserClient::Get()->CanUseCustomSiteInstance();
}
#if defined(OS_MACOSX)
bool App::MoveToApplicationsFolder(mate::Arguments* args) {
  return ui::cocoa::AtomBundleMover::Move(args);
}
bool App::IsInApplicationsFolder() {
  return ui::cocoa::AtomBundleMover::IsCurrentAppInApplicationsFolder();
}
int DockBounce(const std::string& type) {
  int request_id = -1;
  if (type == "critical")
    request_id = Browser::Get()->DockBounce(Browser::BounceType::CRITICAL);
  else if (type == "informational")
    request_id = Browser::Get()->DockBounce(Browser::BounceType::INFORMATIONAL);
  return request_id;
}
void DockSetMenu(atom::api::Menu* menu) {