It appears that the official chrome webstore extension by Rob W is outdated. It was last updated in 2019. 

const preprocessor2 = require("./external/builder/preprocessor2.js");
  const licenseHeader = fs.readFileSync("./src/license_header.js").toString();
  const GLOBALS = "/* eslint-disable */\n";
  const MODIFICATION_WARNING =
    "//\n// THIS FILE IS GENERATED AUTOMATICALLY, DO NOT EDIT MANUALLY!\n//\n";
  const bundleDefines = builder.merge(DEFINES, {
    DEFAULT_PREFERENCES: getDefaultPreferences("mozcentral/"),
  });
  content = preprocessor2.preprocessPDFJSCode(
    {
      rootPath: __dirname,
      defines: bundleDefines,