chrome extensionで外部js(gmail api使いたい)ときの試行錯誤

manifest.json

"content_security_policy": "script-src 'self' https://apis.google.com; object-src 'self'"

とか変えて,

//現在のページにgoogle_api_外部jsを読み込む.
//inject google_api_external_js to current page.
//---------------------------------------
(() => {
  const URI = 'https://apis.google.com/js/client.js?onload=init'
  let head = document.getElementsByTagName('head')[0];
  let script = document.createElement('script');
  script.type = 'text/javascript';
  script.src = URI;
  head.appendChild(script);
})();

現在の読み込んだページにgoogle api jsを読み込ませてcontent_script.jsで認証しようと呼び出ししたら

reference error gapi is not defined.

になる.

アイソレートワールド問題．

[javascript - GAPI Is Not Defined - Stack Overflow] (https://stackoverflow.com/questions/29433744/gapi-is-not-defined)

background.htmlとjsでやればよいらしい.