Controller/Adminhtml/Dashboard/Historic.php
public function execute()
    {
        $output = $this->layoutFactory->create()
            ->createBlock('Fastly\Cdn\Block\Dashboard\Tab\Stats\Historic')
            ->toHtml();
        $resultRaw = $this->resultRawFactory->create();
        return $resultRaw->setContents($output);
    }
public function execute()
    {
        $output = $this->layoutFactory->create()
            ->createBlock('Fastly\Cdn\Block\Dashboard\Tab\Stats\Historic')
            ->toHtml();
        $resultRaw = $this->resultRawFactory->create();
        return $resultRaw->setContents($output);
    }
Return historic stats

@return \Magento\Framework\Controller\Result\Raw