Implement AstBuilder.handleOperatorName.

pkg/front_end/lib/src/fasta/parser/listener.dart

Index: pkg/front_end/lib/src/fasta/parser/listener.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/listener.dart b/pkg/front_end/lib/src/fasta/parser/listener.dart
index d489a1b0eeaf5f4c7dc09f4d12ba627157d3c939..cfbbd5501e1836cc7aa02308adc593ed7661bd75 100644
--- a/pkg/front_end/lib/src/fasta/parser/listener.dart
+++ b/pkg/front_end/lib/src/fasta/parser/listener.dart
@@ -854,6 +854,7 @@ class Listener {
     logEvent("Operator");
   }
 
+  /// Handle the end of a construct of the form "operator <token>".
   void handleOperatorName(Token operatorKeyword, Token token) {
     logEvent("OperatorName");
   }