Tests Storage.getUsageAndQuota with background fetch.

Initial storage
{
  "usage": 0,
  "quota": 1073741824,
  "overrideActive": false,
  "usageBreakdown": [
    {
      "usage": 0,
      "storageType": "file_systems"
    },
    {
      "usage": 0,
      "storageType": "indexeddb"
    },
    {
      "usage": 0,
      "storageType": "cache_storage"
    },
    {
      "usage": 0,
      "storageType": "service_workers"
    }
  ]
}
Registering service worker and background fetch
JS result: fetch success
Storage after background fetch
{
  "usage": 22,
  "quota": 1073741824,
  "overrideActive": false,
  "usageBreakdown": [
    {
      "usage": 0,
      "storageType": "file_systems"
    },
    {
      "usage": 0,
      "storageType": "indexeddb"
    },
    {
      "usage": 0,
      "storageType": "cache_storage"
    },
    {
      "usage": 22,
      "storageType": "service_workers"
    }
  ]
}