extensions/treemap_reporter/treemap_recorder.php
public function paintGroupStart($message, $size)
    {
        parent::paintGroupStart($message, $size);
        $node = new TreemapNode('Group', $message);
        $this->_stack->push($node);
    }
public function paintGroupStart($message, $size)
    {
        parent::paintGroupStart($message, $size);
        $node = new TreemapNode('Group', $message);
        $this->_stack->push($node);
    }
acceptor for start of test group node