requestFileHandles should return an empty list instead of throwing NotFoundError

[beaufortfrancois]

After more thoughts, I believe navigator.crossOriginStorage.requestFileHandles() should NOT throw NotFoundError when COS files are not found. It should simply return an empty list instead.

It's not an exception to not have found files, it's okay to not have them in the cache. A user saying no to the prompt OR an unexpected internal error should indeed throw exceptions.

const hash = {
  algorithm: "SHA-256",
  value: "8f434346648f6b96df89dda901c5176b10a6d83961dd3c1ac88b59b2dc327aa4",
};
let handle;
try {
  [handle] = await navigator.crossOriginStorage.requestFileHandles([hash]);
} catch (err) {
  if (err.name === "NotAllowedError")
    console.log("The user did not grant permission to access the file.");
}
if (handle) {
  const fileBlob = await handle.getFile();
  // Do something with the blob.
} else {
  console.log("The file was not found in Cross-Origin Storage.");
}

[tomayac]

@beaufortfrancois and I discussed this offline. The reason it throws is to remain close to how it works in the Origin Private File System (OPFS):

// --- OPFS ---
await (await navigator.storage.getDirectory()).getFileHandle('i_dont_exist');
// Uncaught NotFoundError: A requested file or directory could not be found at the time an operation was processed.

// --- Cross-Origin Storage ---
await navigator.crossOriginStorage.requestFileHandles([{
  algorithm: 'SHA-256',
  value: '12345678_i_dont_exist_12345678',
}]);
// Uncaught NotFoundError: File "12345678_i_dont_exist_12345678" not found in cross-origin storage.

Originally the requestFileHandles() method was even called getFileHandles(), but we changed it in #4 to include the verb "request" so we could make clear that this could (#47) be an operation that requires prompting. Let's keep this issue open, though.