Use localStorage to store Google Analytics clientId

localstorage-clientid.js

// Check if localStorage is present. It usually is.
if (window.localStorage) {
  ga('create', 'UA-XXXXX-Y', {
    'storage': 'none',
    'clientId': localStorage.getItem('GA_CLIENT_ID_HASHED')
  });
} else {
  ga('create', 'UA-XXXXX-Y', 'auto');
}

ga('send', 'pageview');