How to rewrite the 'content-security-policy' HTTP header to work around bugs in the Chrome extension APIs: https://www.mixmax.com/blog/what-to-do-when-your-app-breaks

rewrite_CSP_header.js

var hosts = 'https://d1j5o6e2vipffp.cloudfront.net';
var iframeHosts = 'https://app.mixmax.com';

chrome.webRequest.onHeadersReceived.addListener(function(details) {
  for (var i = 0; i < details.responseHeaders.length; i++) {
    var isCSPHeader = /content-security-policy/i.test(details.responseHeaders[i].name);
    if (isCSPHeader) {
      var csp = details.responseHeaders[i].value;
      csp = csp.replace('script-src', 'script-src ' + hosts);
      csp = csp.replace('style-src', 'style-src ' + hosts);
      csp = csp.replace('frame-src', 'frame-src ' + iframeHosts);
      details.responseHeaders[i].value = csp;
    }
  }

  return {
    responseHeaders: details.responseHeaders
  };
}, {
  urls: ['https://mail.google.com/*'],
  types: ['main_frame']
}, ['blocking', 'responseHeaders']);