getDevicePixelRatio.js

  window.getDevicePixelRatio = function () {
    var ratio = 1;
    // To account for zoom, change to use deviceXDPI instead of systemXDPI
    if (window.screen.systemXDPI !== undefined && window.screen.logicalXDPI !== undefined && window.screen.systemXDPI > window.screen.logicalXDPI) {
      // Only allow for values > 1
      ratio = window.screen.systemXDPI / window.screen.logicalXDPI;
    }
    else if (window.devicePixelRatio !== undefined) {
      ratio = window.devicePixelRatio;
    }
    return ratio;
  };

  ga('create', '{{ settings.GOOGLE_ANALYTICS_TRACKING_ID }}', 'auto', opt_configObject);
  ga('set', 'dimension2', getDevicePixelRatio().toFixed(2));