* 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/mac/atom_application.h
AVF_EXPORT AVMediaType const AVMediaTypeAudio;
typedef NS_ENUM(NSInteger, AVAuthorizationStatusMac) {
  AVAuthorizationStatusNotDeterminedMac = 0,
  AVAuthorizationStatusRestrictedMac = 1,
  AVAuthorizationStatusDeniedMac = 2,
  AVAuthorizationStatusAuthorizedMac = 3,
};
@interface NSMenuItem (HighSierraSDK)
@property(atomic, readwrite)
    BOOL allowsKeyEquivalentWhenHidden API_AVAILABLE(macosx(10.13));
- (void)setAllowsKeyEquivalentWhenHidden:(BOOL)arg1
    API_AVAILABLE(macosx(10.13));
@end
@interface AVCaptureDevice (MojaveSDK)
+ (void)requestAccessForMediaType:(AVMediaType)mediaType
                completionHandler:(void (^)(BOOL granted))handler
    API_AVAILABLE(macosx(10.14));
+ (AVAuthorizationStatusMac)authorizationStatusForMediaType:
    (AVMediaType)mediaType API_AVAILABLE(macosx(10.14));
@end
@interface NSColor (MojaveSDK)
@property(class, strong, readonly)
    NSColor* controlAccentColor API_AVAILABLE(macosx(10.14));
@property(class, strong, readonly)
    NSColor* systemBlueColor API_AVAILABLE(macosx(10.10));
@property(class, strong, readonly)
    NSColor* systemBrownColor API_AVAILABLE(macosx(10.10));
@property(class, strong, readonly)
    NSColor* systemGrayColor API_AVAILABLE(macosx(10.10));
@property(class, strong, readonly)