This is to track all the work to implement ServiceWorkerContainer mojo interface.
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Roughly corresponds to navigator.serviceWorker. Actually needed for anything that could access a ServiceWorkerRegistration/ServiceWorker. E.g., SW needs this since it has self.registration, even though we don’t implement navigator.serviceWorker for Worker yet. But eventually anything that can touch these objects should be a ServiceWorkerContainer, so it’s OK to use this name.

When the browser initialized the navigation or SW startup, it should send the SWContainer along.

interface ServiceWorkerContainer {
  SetController(ServiceWorkerObject controller);
  ServiceWorkerStateChanged(ServiceWorkerObject);
  ServiceWorkerRegistrationUpdateFound(ServiceWorkerRegistrationObject)
  PostMessage();
};
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