Function installExtension

src/runtime.js:210–228

* @param {function(!Object,!Object)|!ExtensionPayload} fnOrStruct

(fnOrStruct)

   * @param {function(!Object,!Object)|!ExtensionPayload} fnOrStruct
   */
  function installExtension(fnOrStruct) {
    const register = () => {
      iniPromise.then(() => {
        if (typeof fnOrStruct == 'function') {
          fnOrStruct(global.AMP, global.AMP._);
        } else {
          extensions.registerExtension(
            fnOrStruct.n,
            fnOrStruct.ev,
            fnOrStruct.l,
            fnOrStruct.f,
            global.AMP
          );
        }
      });
    };

    startRegisterOrChunk(global, fnOrStruct, register);
  }

  // Handle high priority extensions now, and if necessary issue
  // requests for new extensions (used for experimental version