MDL-55224 core: Import PHP-CSS-Parser into core

Part of MDL-55071

lib/php-css-parser/Value/CSSString.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Sabberworm\CSS\Value;
+
+class CSSString extends PrimitiveValue {
+
+	private $sString;
+
+	public function __construct($sString, $iLineNo = 0) {
+		$this->sString = $sString;
+		parent::__construct($iLineNo);
+	}
+
+	public function setString($sString) {
+		$this->sString = $sString;
+	}
+
+	public function getString() {
+		return $this->sString;
+	}
+
+	public function __toString() {
+		return $this->render(new \Sabberworm\CSS\OutputFormat());
+	}
+
+	public function render(\Sabberworm\CSS\OutputFormat $oOutputFormat) {
+		$sString = addslashes($this->sString);
+		$sString = str_replace("\n", '\A', $sString);
+		return $oOutputFormat->getStringQuotingType() . $sString . $oOutputFormat->getStringQuotingType();
+	}
+
+}