code/Debug/Model/Service.php
public function setTemplateHints($status)
    {
        $this->deleteTemplateHintsDbConfigs();

        $config = $this->getConfig();
        $config->saveConfig('dev/debug/template_hints', (int)$status);
        $config->saveConfig('dev/debug/template_hints_blocks', (int)$status);
    }
public function setTemplateHints($status)
    {
        $this->deleteTemplateHintsDbConfigs();

        $config = $this->getConfig();
        $config->saveConfig('dev/debug/template_hints', (int)$status);
        $config->saveConfig('dev/debug/template_hints_blocks', (int)$status);
    }
Changes status for template and block hints

@param int $status