function detectBrowser(window) {
  // Returned result object.
  var result = {
    browser: null,
    version: null
  };

  // Fail early if it's not a browser
  if (typeof window === 'undefined' || !window.navigator || !window.navigator.userAgent) {
    result.browser = 'Not a browser.';
    return result;
  }
  var navigator = window.navigator;
  if (navigator.mozGetUserMedia) {
    // Firefox.
    result.browser = 'firefox';
    result.version = extractVersion(navigator.userAgent, /Firefox\/(\d+)\./, 1);
  } else if (navigator.webkitGetUserMedia || window.isSecureContext === false && window.webkitRTCPeerConnection) {
    // Chrome, Chromium, Webview, Opera.
    // Version matches Chrome/WebRTC version.
    // Chrome 74 removed webkitGetUserMedia on http as well so we need the
    // more complicated fallback to webkitRTCPeerConnection.
    result.browser = 'chrome';
    result.version = extractVersion(navigator.userAgent, /Chrom(e|ium)\/(\d+)\./, 2);
  } else if (window.RTCPeerConnection && navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
    // Safari.
    result.browser = 'safari';
    result.version = extractVersion(navigator.userAgent, /AppleWebKit\/(\d+)\./, 1);
    result.supportsUnifiedPlan = window.RTCRtpTransceiver && 'currentDirection' in window.RTCRtpTransceiver.prototype;
  } else {
    // Default fallthrough: not supported.
    result.browser = 'Not a supported browser.';
    return result;
  }
  return result;
}
Browser detector.

@return {object} result containing browser and version
    properties.