function parseExtensionURL(url) {
    url = url.substring(CRX_BASE_URL.length);
    // Find the (url-encoded) colon and verify that the scheme is allowed.
    var schemeIndex = url.search(/:|%3A/i);
    if (schemeIndex === -1) {
      return undefined;
    }
    var scheme = url.slice(0, schemeIndex).toLowerCase();
    if (schemes.includes(scheme)) {
      // NOTE: We cannot use the `updateUrlHash` function in this context.
      url = url.split("#", 1)[0];
      if (url.charAt(schemeIndex) === ":") {
        url = encodeURIComponent(url);
      }
      return url;
    }
    return undefined;
  }
@param {string} url The URL prefixed with chrome-extension://.../
@returns {string|undefined} The percent-encoded URL of the (PDF) file.