create "[]" token as SymbolToken

pkg/compiler/lib/src/parser/node_listener.dart

Index: pkg/compiler/lib/src/parser/node_listener.dart
diff --git a/pkg/compiler/lib/src/parser/node_listener.dart b/pkg/compiler/lib/src/parser/node_listener.dart
index ecb38f4cca1ddfa1bb0b1911394e3e5b686df1a0..347e6a6f515c01b0f665f2393096f8a84c5cbeae 100644
--- a/pkg/compiler/lib/src/parser/node_listener.dart
+++ b/pkg/compiler/lib/src/parser/node_listener.dart
@@ -8,7 +8,7 @@ import 'package:front_end/src/fasta/parser/parser.dart'
     show FormalParameterType;
 import 'package:front_end/src/fasta/parser/identifier_context.dart'
     show IdentifierContext;
-import 'package:front_end/src/fasta/scanner.dart' show StringToken, Token;
+import 'package:front_end/src/fasta/scanner.dart' show SymbolToken, Token;
 import 'package:front_end/src/scanner/token.dart' show TokenType;
 
 import '../common.dart';
@@ -718,8 +718,8 @@ class NodeListener extends ElementListener {
     NodeList arguments =
         makeNodeList(1, openSquareBracket, closeSquareBracket, null);
     Node receiver = popNode();
-    Token token = new StringToken.fromString(
-        TokenType.INDEX, '[]', openSquareBracket.charOffset);
+    Token token =
+        new SymbolToken(TokenType.INDEX, openSquareBracket.charOffset);
     Node selector = new Operator(token);
     pushNode(new Send(receiver, selector, arguments));
   }