browser.menus.create({
  id: "tab-rename",
  title: "Rename",
  contexts: ["tab"],
}, function() {
  if (browser.runtime.lastError) {
    console.log(`Error: ${browser.runtime.lastError}`);
  }
});

let tabRename = `
  var newTitle = window.prompt("", document.title);
  if (newTitle) { document.title = newTitle; }
`;

browser.menus.onClicked.addListener((info, tab) => {
  if (info.menuItemId == "tab-rename") {
    browser.tabs.update(tab.id, { active: true });
    browser.tabs.executeScript(tab.id, { code: tabRename });
  }
});