add fasta.scanner support for lazy assignment operators

pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart

 // Copyright (c) 2011, 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 fasta.scanner.array_based_scanner;
 
 import 'error_token.dart' show ErrorToken, UnmatchedToken;
 
 import '../../scanner/token.dart'
     show Keyword, KeywordTokenWithComment, Token, TokenType;
@@ skipping 11 matching lines @@
 import 'characters.dart' show $LF, $STX;
 
 import 'abstract_scanner.dart' show AbstractScanner, closeBraceInfoFor;
 
 import '../util/link.dart' show Link;
 
 abstract class ArrayBasedScanner extends AbstractScanner {
   bool hasErrors = false;
 
   ArrayBasedScanner(bool includeComments, bool scanGenericMethodComments,
-      {int numberOfBytesHint})
+      bool scanLazyAssignmentOperators, {int numberOfBytesHint})
       : super(includeComments, scanGenericMethodComments,
+            scanLazyAssignmentOperators,
             numberOfBytesHint: numberOfBytesHint);
 
   /**
    * The stack of open groups, e.g [: { ... ( .. :]
    * Each BeginGroupToken has a pointer to the token where the group
    * ends. This field is set when scanning the end group token.
    */
   Link<BeginGroupToken> groupingStack = const Link<BeginGroupToken>();
 
   /**
@@ skipping 250 matching lines @@
     //      |
     //     next
     //      v
     //     EOF
     TokenType type = closeBraceInfoFor(begin);
     appendToken(new SyntheticSymbolToken(type, tokenStart, comments));
     begin.endGroup = tail;
     appendErrorToken(new UnmatchedToken(begin));
   }
 }