Piwik\AssetManager\UIAssetMerger\StylesheetUIAssetMerger::processFileContent PHP Method

    protected function processFileContent($uiAsset)
    {
        $pathsRewriter = $this->getCssPathsRewriter($uiAsset);
        $content = $uiAsset->getContent();
        $content = $this->rewriteCssImagePaths($content, $pathsRewriter);
        $content = $this->rewriteCssImportPaths($content, $pathsRewriter);
        return $content;
    }