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let disable: WebAPI.ServiceWorkerAPI.navigationPreloadManager => promise< unit,>
let enable: WebAPI.ServiceWorkerAPI.navigationPreloadManager => promise< unit,>
let getState: WebAPI.ServiceWorkerAPI.navigationPreloadManager => promise< WebAPI.ServiceWorkerAPI.navigationPreloadState,>
let setHeaderValue: ( WebAPI.ServiceWorkerAPI.navigationPreloadManager, string,) => promise<unit>