I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

Right now, Service Worker package do not have sync feature. Since Angular follows a plugin mechanism to add service worker apis, I feel this is a major feature which is required.

Background Sync

Expected behavior

Should be able to register a background sync easily using @angular/service-worker package.

Minimal reproduction of the problem with instructions

N/A

What is the motivation / use case for changing the behavior?

This is required to make sure that user is able to do actions even on unstable internet connections.