Mark some unused code as being deprecated

pkg/analyzer/lib/src/generated/incremental_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.
 
+@deprecated
 library analyzer.src.generated.incremental_scanner;
 
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart' show TokenMap;
 
 /**
  * An `IncrementalScanner` is a scanner that scans a subset of a string and
  * inserts the resulting tokens into the middle of an existing token stream.
  */
+@deprecated
 class IncrementalScanner {
   /**
    * The source being scanned.
    */
   final Source source;
 
   /**
    * The reader used to access the characters in the source.
    */
   final CharacterReader reader;
@@ skipping 209 matching lines @@
       while (comment != null) {
         comment.offset += delta;
         comment = comment.next;
       }
       token = token.next;
     }
     _tokenMap.put(token, token);
     token.offset += delta;
   }
 }