src/content_scripts/profile_inject.js

chrome.storage.sync.get(null, function(items) {
  if (items.history &&
      document.querySelector('.user-profile__user-links') === null) {
    var nameElement = document.querySelector('.user-profile__user-name');
    if (nameElement !== null) {
      var name = encodeURIComponent(nameElement.innerHTML);
      var link = document.location.pathname.split('/profile')[0] +
          '/threads?thread_filter=(creator:%22' + name + '%22+%7C+replier:%22' +
          name + '%22)';
      document.querySelector('.user-profile__user-details-container')
          .insertAdjacentHTML(
              'beforeend',
              '<div class="user-profile__user-links"><div class="user-profile__user-link-title">' +
                  chrome.i18n.getMessage('inject_links') +
                  '</div><ul><li class="user-profile__user-link"><a href="' +
                  link + '" data-stats-id="my-posts-link">' +
                  chrome.i18n.getMessage('inject_previousposts') +
                  '</a></li></ul></div>');
    }
  }
});