Add StringScanner.scanChar() and .expectChar().

test/line_scanner_test.dart

Index: test/line_scanner_test.dart
diff --git a/test/line_scanner_test.dart b/test/line_scanner_test.dart
index 9874cb309461304aa0f250797b28016df1059e13..ed04b371c1e4b713e967c3c3a51c0f99a5b06095 100644
--- a/test/line_scanner_test.dart
+++ b/test/line_scanner_test.dart
@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:charcode/charcode.dart';
 import 'package:string_scanner/string_scanner.dart';
 import 'package:test/test.dart';
 
@@ -80,6 +81,39 @@ void main() {
     });
   });
 
+  group("scanChar()", () {
+    test("on a non-newline character increases the column but not the line",
+        () {
+      scanner.scanChar($f);
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(1));
+    });
+
+    test("consuming a newline resets the column and increases the line", () {
+      scanner.expect('foo');
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(3));
+
+      scanner.scanChar($lf);
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(0));
+    });
+
+    test("consuming halfway through a CR LF doesn't count as a line", () {
+      scanner.expect('foo\nbar');
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(3));
+
+      scanner.scanChar($cr);
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(4));
+
+      scanner.scanChar($lf);
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(0));
+    });
+  });
+
   group("position=", () {
     test("forward through newlines sets the line and column", () {
       scanner.position = 10; // "foo\nbar\r\nb"