pkg/string_scanner: code format, expanded dependency constraint on unittest

test/string_scanner_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library string_scanner.string_scanner_test;
 
 import 'package:string_scanner/string_scanner.dart';
 import 'package:unittest/unittest.dart';
 
 void main() {
@@ skipping 312 matching lines @@
       expect(scanner.position, equals(4));
       expect(scanner.rest, equals('bar'));
     });
 
     test('throws an ArgumentError if the position is -1', () {
       expect(() => new StringScanner('foo bar', position: -1),
           throwsArgumentError);
     });
 
     test('throws an ArgumentError if the position is beyond the string', () {
-      expect(() => new StringScanner('foo bar', position: 8),
-          throwsArgumentError);
+      expect(
+          () => new StringScanner('foo bar', position: 8), throwsArgumentError);
     });
   });
 }