Css/StyleAggregate.php
protected function rewritePaths(array $styles)
    {
        foreach ($styles as &$style) {
            /** @var $resource MaterializedResource */
            $resource = $style['resource'];
            $replaceCallback = function ($match) use ($resource) {
                return "url('".$resource->resolvePath($match[1])."')";
            };
            $style['content'] = preg_replace_callback(ResourceScanner::PATH_PATTERN, $replaceCallback, $style['content']);
        }
        return $styles;
    }
protected function rewritePaths(array $styles)
    {
        foreach ($styles as &$style) {
            /** @var $resource MaterializedResource */
            $resource = $style['resource'];
            $replaceCallback = function ($match) use ($resource) {
                return "url('".$resource->resolvePath($match[1])."')";
            };
            $style['content'] = preg_replace_callback(ResourceScanner::PATH_PATTERN, $replaceCallback, $style['content']);
        }
        return $styles;
    }
Rewrites the paths of referenced resources.