* 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/browser.h
#ifndef ATOM_BROWSER_BROWSER_H_
#define ATOM_BROWSER_BROWSER_H_
#include <memory>
#include <string>
#include <vector>
#include "atom/browser/browser_observer.h"
#include "atom/browser/window_list_observer.h"
#include "atom/common/promise_util.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/observer_list.h"
#include "base/strings/string16.h"
#include "base/values.h"
#include "native_mate/arguments.h"
#if defined(OS_WIN)
#include <windows.h>
#include "base/files/file_path.h"
#endif
namespace base {
class FilePath;
}
namespace gfx {
class Image;
}
namespace atom {
class AtomMenuModel;