update fasta scanner to always generate INDEX or INDEX_EQ tokens

pkg/front_end/test/scanner_fasta_test.dart

Index: pkg/front_end/test/scanner_fasta_test.dart
diff --git a/pkg/front_end/test/scanner_fasta_test.dart b/pkg/front_end/test/scanner_fasta_test.dart
index 933e3897eff206c0a386d5e6dd8b6d58c25aa286..9744a3c232dfae3b58dc357b8671c9cf1efd9037 100644
--- a/pkg/front_end/test/scanner_fasta_test.dart
+++ b/pkg/front_end/test/scanner_fasta_test.dart
@@ -157,22 +157,6 @@ class ScannerTest_Fasta extends ScannerTestBase {
 
   @override
   @failingTest
-  void test_index() {
-    // TODO(paulberry,ahe): "[]" should be parsed as a single token.
-    // See dartbug.com/28665.
-    super.test_index();
-  }
-
-  @override
-  @failingTest
-  void test_index_eq() {
-    // TODO(paulberry,ahe): "[]=" should be parsed as a single token.
-    // See dartbug.com/28665.
-    super.test_index_eq();
-  }
-
-  @override
-  @failingTest
   void test_mismatched_closer() {
     // TODO(paulberry,ahe): Fasta and analyzer recover this error differently.
     // Figure out which recovery technique we want the front end to use.