Credential Management API + `https://myaccount.nytimes.com`

Sign-In.js

// On https://myaccount.nytimes.com/mobile/login/smart/index.html

navigator.credentials.get({password: true}) // Include `{ ..., 'unmediated': true }` to grab credentials w/o chooser
  .then(c => {
    if (!c)
      return;
    c.additionalData = new FormData(document.querySelector('.loginForm'));
    c.idName = "userid";
    fetch('/mobile/login/smart/index.html', { credentials: c, method:'POST' })
      .then(r => window.location = 'http://mobile.nytimes.com');
  });

Store.js

// Assuming that the sign-in form is mildly adjusted to include `autocomplete` attributes:
//
// <form ...>
//   ...
//   <input type="text" id="userid" name="userid" autocomplete="username" ...>
//   ...
//   <input type="password" id="password" name="password" autocomplete="current-password" ...>
//   ...
// </form>
document.querySelector('input[name=username]').setAttribute('autocomplete', 'username');
document.querySelector('input[name=password]').setAttribute('autocomplete', 'current-password');
document.querySelector('.loginForm').addEventListener('submit', e => {
  if (!navigator.credentials)
    return;
  e.preventDefault();
  var c = new PasswordCredential(e.target);
  fetch('/mobile/login/smart/index.html', { credentials: c, method: 'POST' })
    .then(r => {
      if (r.type == 'opaqueredirect') { // If we're redirected, yay! Store the credential.
        navigator.credentials.store(c).then(_ => {
          window.location = 'http://mobile.nytimes.com';
        });
      }
    });
});