Add a DataUri class.

lib/src/scan.dart

Index: lib/src/scan.dart
diff --git a/lib/src/scan.dart b/lib/src/scan.dart
index d675b8b41c9e033c3aafdb339e31a59ac8d17832..9710d7c8bb7e596443500cae93f9429b15b6ca68 100644
--- a/lib/src/scan.dart
+++ b/lib/src/scan.dart
@@ -75,3 +75,9 @@ String expectQuotedString(StringScanner scanner, {String name}) {
       .substring(1, string.length - 1)
       .replaceAllMapped(_quotedPair, (match) => match[1]);
 }
+
+bool scanPercentToken(StringScanner scanner) {
+  var position = scanner.position;
+  if (!scanner.scan(token)) return false;
+  var token = 

[kevmoo, 2015/10/19 22:45:21]

this looks very broken

[nweiz, 2015/10/19 23:08:32]

Done.

+}