Add percentage matching since keyframe steps are treated as regular selectors

Author: raxbg

lib/Sabberworm/CSS/Property/Selector.php

@@ -41,13 +41,12 @@ class Selector {
 	private $iSpecificity;
 
 	public static function isValid($sSelector) {
-		return preg_match("/^[a-zA-Z0-9\x{00A0}-\x{FFFF}_\^\$\|\*\=\"\'\~\[\]\(\)\-\s\.:#\+\>]*$/u", $sSelector);
+		return preg_match("/^([a-zA-Z0-9\x{00A0}-\x{FFFF}_\^\$\|\*\=\"\'\~\[\]\(\)\-\s\.:#\+\>]*|\s*?[\+-]?\d+\%\s*)$/u", $sSelector);
 	}
 
 	public function __construct($sSelector, $bCalculateSpecificity = false) {
 		if (!Selector::isValid($sSelector)) {
-			preg_match("/[^a-zA-Z0-9\x{00A0}-\x{FFFF}_\^\$\|\*\=\"\'\~\[\]\(\)\-\s\.:#\+\>]/u", $sSelector, $matches);
-			throw new UnexpectedTokenException("Selector did not match '/^[a-zA-Z0-9\x{00A0}-\x{FFFF}_\^\$\|\*\=\"\'\~\[\]\(\)\-\s\.:#\+\>]*$/u'. ({$matches[0]} found).", $sSelector, "custom");
+			throw new UnexpectedTokenException("Selector did not match '/^([a-zA-Z0-9\x{00A0}-\x{FFFF}_\^\$\|\*\=\"\'\~\[\]\(\)\-\s\.:#\+\>]*|\s*?[\+-]?\d+\%\s*)$/u'.", $sSelector, "custom");
 		}
 		$this->setSelector($sSelector);
 		if ($bCalculateSpecificity) {