* 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
void OpenURL(const std::string& url);
#if defined(OS_MACOSX)
  
  void NewWindowForTab();
#endif  
  
  
  void Activate(bool has_visible_windows);
  bool IsEmojiPanelSupported();
  
  void WillFinishLaunching();
  void DidFinishLaunching(const base::DictionaryValue& launch_info);
  void OnAccessibilitySupportChanged();
  
  void RequestLogin(scoped_refptr<LoginHandler> login_handler,
                    std::unique_ptr<base::DictionaryValue> request_details);
  void PreMainMessageLoopRun();
  
  
  void SetMainMessageLoopQuitClosure(base::OnceClosure quit_closure);
  void AddObserver(BrowserObserver* obs) { observers_.AddObserver(obs); }
  void RemoveObserver(BrowserObserver* obs) { observers_.RemoveObserver(obs); }
  bool is_shutting_down() const { return is_shutdown_; }
  bool is_quiting() const { return is_quiting_; }
  bool is_ready() const { return is_ready_; }
  const util::Promise& WhenReady(v8::Isolate* isolate);
 protected:
  
  std::string GetExecutableFileVersion() const;