text: import browser from 'webextension-polyfill';
  
  const message = 'Add contribPageLastOpen';
  
  const revision = 'ryY8H0EWf';
  const downRevision = 'HJ5MKKGhW';
  
  const storage = browser.storage.local;
  
  async function upgrade() {
    const changes = {};
    changes.contribPageLastOpen = 0;
  
    changes.storageVersion = revision;
    return storage.set(changes);
  }
  
  async function downgrade() {
    const changes = {};
    await storage.remove('contribPageLastOpen');
  
    changes.storageVersion = downRevision;
    return storage.set(changes);
  }
  
  module.exports = {
    message,
    revision,
    upgrade,
    downgrade
  };
  