constructor(page) {
		const url = page.url;
		this.location_ = url.endsWith('/') ? url : url + '/';
		this.data_ = JSON.stringify(page || {});
	}
We cache a non SSRed page in service worker so that there is
no flash of content when user lands on routes other than `/`.
And we dont have to cache every single html file.
Go easy on network usage of clients.