add fasta.scanner support for lazy assignment operators

pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart

 // Copyright (c) 2013, 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.utf8_bytes_scanner;
 
 import 'dart:convert' show UNICODE_BOM_CHARACTER_RUNE, UTF8;
 
 import '../../scanner/token.dart' show TokenType;
 
@@ skipping 62 matching lines @@
   /**
    * Creates a new Utf8BytesScanner. The source file is expected to be a
    * [Utf8BytesSourceFile] that holds a list of UTF-8 bytes. Otherwise the
    * string text of the source file is decoded.
    *
    * The list of UTF-8 bytes [file.slowUtf8Bytes()] is expected to return an
    * array whose last element is '0' to signal the end of the file. If this
    * is not the case, the entire array is copied before scanning.
    */
   Utf8BytesScanner(this.bytes,
-      {bool includeComments: false, bool scanGenericMethodComments: false})
+      {bool includeComments: false,
+      bool scanGenericMethodComments: false,
+      bool scanLazyAssignmentOperators: false})
       : super(includeComments, scanGenericMethodComments,
+            scanLazyAssignmentOperators,
             numberOfBytesHint: bytes.length) {
     assert(bytes.last == 0);
     // Skip a leading BOM.
     if (containsBomAt(0)) byteOffset += 3;
   }
 
   bool containsBomAt(int offset) {
     const BOM_UTF8 = const [0xEF, 0xBB, 0xBF];
 
     return offset + 3 < bytes.length &&
@@ skipping 119 matching lines @@
 
   @override
   DartDocToken createDartDocToken(TokenType type, int start, bool asciiOnly,
       [int extraOffset = 0]) {
     return new DartDocToken.fromUtf8Bytes(
         type, bytes, start, byteOffset + extraOffset, asciiOnly, tokenStart);
   }
 
   bool atEndOfFile() => byteOffset >= bytes.length - 1;
 }