update fasta scanner to generate two types of comments

pkg/front_end/test/token_test.dart

 // Copyright (c) 2017, 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.
 
 import 'package:front_end/src/fasta/scanner/string_scanner.dart';
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/scanner/token.dart';
 import 'package:front_end/src/scanner/reader.dart' as analyzer;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
@@ skipping 11 matching lines @@
   void test_applyDelta() {
     var scanner = new StringScanner('/* 1 */ foo', includeComments: true);
     var token = scanner.tokenize();
     expect(token.offset, 8);
     expect(token.precedingComments.offset, 0);
     token.applyDelta(12);
     expect(token.offset, 20);
     expect(token.precedingComments.offset, 12);
   }
 
+  void test_comments() {
+    var source = '''
+/// Single line dartdoc comment
+class Foo {
+  /**
+   * Multi-line dartdoc comment
+   */
+  void bar() {
+    // Single line comment
+    int x = 0;
+    /* Multi-line comment */
+    x = x + 1;
+  }
+}
+''';
+    var scanner = new StringScanner(source, includeComments: true);
+    fasta.Token token = scanner.tokenize();
+
+    Token nextComment() {
+      while (!token.isEof) {
+        Token comment = token.precedingComments;
+        token = token.next;
+        if (comment != null) return comment;
+      }
+      return null;
+    }
+
+    fasta.Token comment = nextComment();
+    expect(comment.lexeme, contains('Single line dartdoc comment'));
+    expect(comment.type, TokenType.SINGLE_LINE_COMMENT);
+
+    comment = nextComment();
+    expect(comment.lexeme, contains('Multi-line dartdoc comment'));
+    expect(comment.type, TokenType.MULTI_LINE_COMMENT);
+
+    comment = nextComment();
+    expect(comment.lexeme, contains('Single line comment'));
+    expect(comment.type, TokenType.SINGLE_LINE_COMMENT);
+
+    comment = nextComment();
+    expect(comment.lexeme, contains('Multi-line comment'));
+    expect(comment.type, TokenType.MULTI_LINE_COMMENT);
+  }
+
   void test_copy() {
     String source = '/* 1 */ /* 2 */ main() {print("hello"); return;}';
     int commentCount = 0;
 
     void assertCopiedToken(Token token1, Token token2) {
       if (token1 == null) {
         expect(token2, isNull);
         return;
       }
       expect(token1.lexeme, token2.lexeme);
@@ skipping 74 matching lines @@
     token = token.next;
     expect(token.lexeme, '&');
     expect(token.value(), '&');
     // String tokens
     token = token.next;
     print('String token :: ${token.runtimeType}');
     expect(token.lexeme, '"home"');
     expect(token.value(), '"home"');
   }
 }