code: public function onOutput(Event $event)
      {
          $this->channelName = $this->debug->getCfg('channel');
          $this->data = $this->debug->getData();
          $this->processAlerts();
          $this->processSummary();
          $this->processLog();
          if ($this->json['rows']) {
              \array_unshift($this->json['rows'], array(
                  array('PHP', isset($_SERVER['REQUEST_METHOD'])
                      ? $_SERVER['REQUEST_METHOD'].' '.$_SERVER['REQUEST_URI']
                      : '$: '. \implode(' ', $_SERVER['argv'])
                  ),
                  null,
                  'groupCollapsed',
              ));
              \array_push($this->json['rows'], array(
                  array(),
                  null,
                  'groupEnd',
              ));
              $encoded = $this->encode($this->json);
              if (\strlen($encoded) > 250000) {
                  $this->debug->warn('chromeLogger: output limit exceeded');
              } else {
                  $event['headers'][] = array(self::HEADER_NAME, $encoded);
              }
          }
          $this->data = array();
          $this->json['rows'] = array();
      }
docs: Output the log as chromelogger headers
  
  @param Event $event debug.output event object
  
  @return void