Issue 23919. Fix for line starts in multiline comments.

pkg/analyzer/lib/src/generated/scanner.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 engine.scanner;
 
 import 'dart:collection';
 
 import 'error.dart';
 import 'java_engine.dart';
@@ skipping 1483 matching lines @@
           next = _reader.advance();
           ++nesting;
         }
       } else if (next == 0xD) {
         next = _reader.advance();
         if (next == 0xA) {
           next = _reader.advance();
         }
         recordStartOfLine();
       } else if (next == 0xA) {
+        next = _reader.advance();
         recordStartOfLine();
-        next = _reader.advance();
       } else {
         next = _reader.advance();
       }
     }
   }
 
   int _tokenizeMultiLineRawString(int quoteChar, int start) {
     int next = _reader.advance();
     outer: while (next != -1) {
       while (next != quoteChar) {
@@ skipping 1146 matching lines @@
   CommentToken get precedingComments => _precedingComment;
 
   void set precedingComments(CommentToken comment) {
     _precedingComment = comment;
     _setCommentParent(_precedingComment);
   }
 
   @override
   Token copy() => new TokenWithComment(type, offset, precedingComments);
 }