improve fasta unterminated string recovery

pkg/front_end/test/scanner_replacement_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 'dart:convert' show UTF8;
 
 import 'package:front_end/src/fasta/scanner/recover.dart'
     show defaultRecoveryStrategy;
 import 'package:front_end/src/fasta/scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
@@ skipping 174 matching lines @@
     expect(closeParen1.isSynthetic, isTrue);
     expect(openBrace.endToken, same(closeBrace));
     expect(closeBrace.isSynthetic, isFalse);
     expect(openParen2.endToken, same(closeParen2));
     expect(closeParen2.isSynthetic, isTrue);
     expect(eof.isEof, isTrue);
   }
 
   @override
   @failingTest
-  void test_string_multi_unterminated() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_multi_unterminated();
-  }
-
-  @override
-  @failingTest
   void test_string_multi_unterminated_interpolation_block() {
     // See defaultRecoveryStrategy recoverString
     super.test_string_multi_unterminated_interpolation_block();
   }
 
   @override
   @failingTest
   void test_string_multi_unterminated_interpolation_identifier() {
     // See defaultRecoveryStrategy recoverString
     super.test_string_multi_unterminated_interpolation_identifier();
   }
 
   @override
   @failingTest
-  void test_string_raw_multi_unterminated() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_raw_multi_unterminated();
-  }
-
-  @override
-  @failingTest
-  void test_string_raw_simple_unterminated_eof() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_raw_simple_unterminated_eof();
-  }
-
-  @override
-  @failingTest
-  void test_string_raw_simple_unterminated_eol() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_raw_simple_unterminated_eol();
-  }
-
-  @override
-  @failingTest
   void test_string_simple_interpolation_missingIdentifier() {
     // See defaultRecoveryStrategy recoverStringInterpolation
     super.test_string_simple_interpolation_missingIdentifier();
   }
 
   @override
   @failingTest
   void test_string_simple_interpolation_nonIdentifier() {
     // See defaultRecoveryStrategy recoverStringInterpolation
     super.test_string_simple_interpolation_nonIdentifier();
   }
 
   @override
   @failingTest
-  void test_string_simple_unterminated_eof() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_simple_unterminated_eof();
-  }
-
-  @override
-  @failingTest
-  void test_string_simple_unterminated_eol() {
-    // See defaultRecoveryStrategy recoverString
-    super.test_string_simple_unterminated_eol();
-  }
-
-  @override
-  @failingTest
   void test_string_simple_unterminated_interpolation_block() {
     // See defaultRecoveryStrategy recoverString
     super.test_string_simple_unterminated_interpolation_block();
   }
 
   @override
   @failingTest
   void test_string_simple_unterminated_interpolation_identifier() {
     // See defaultRecoveryStrategy recoverString
     super.test_string_simple_unterminated_interpolation_identifier();
@@ skipping 90 matching lines @@
       } else if (token is fasta.UnmatchedToken) {
         expect(lastClosedGroup?.endGroup?.next, same(token),
             reason: 'Unexpected error token for group: $lastClosedGroup');
         expect(token.begin, lastClosedGroup);
       }
       token = token.next;
     }
     expect(openerStack, isEmpty, reason: 'Missing closers');
   }
 }