static async getRawCsps(artifacts, context) {
    const devtoolsLog = artifacts.DevtoolsLog;
    const mainResource = await MainResource.request({devtoolsLog, URL: artifacts.URL}, context);

    const cspMetaTags = artifacts.MetaElements
      .filter(m => {
        return m.httpEquiv && m.httpEquiv.toLowerCase() === 'content-security-policy';
      })
      .flatMap(m => (m.content || '').split(','))
      .filter(rawCsp => rawCsp.replace(/\s/g, ''));
    const cspHeaders = mainResource.responseHeaders
      .filter(h => {
        return h.name.toLowerCase() === 'content-security-policy';
      })
      .flatMap(h => h.value.split(','))
      .filter(rawCsp => rawCsp.replace(/\s/g, ''));

    return {cspHeaders, cspMetaTags};
  }
@param {LH.Artifacts} artifacts
@param {LH.Audit.Context} context
@return {Promise<{cspHeaders: string[], cspMetaTags: string[]}>}