Use FastaMessage instead of String. Part 1.

pkg/front_end/lib/src/fasta/source/stack_listener.dart

Index: pkg/front_end/lib/src/fasta/source/stack_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/stack_listener.dart b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
index 18cfd42cea03f5112ac42b95364e052fc6245152..45f81d134b03043e039484318c611cc63dd5733f 100644
--- a/pkg/front_end/lib/src/fasta/source/stack_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
@@ -4,7 +4,7 @@
 
 library fasta.stack_listener;
 
-import '../fasta_codes.dart' show FastaMessage;
+import '../fasta_codes.dart' show BoundFastaMessage, FastaMessage;
 
 import '../parser.dart' show Listener, MemberKind;
 
@@ -277,6 +277,10 @@ abstract class StackListener extends Listener {
   void deprecated_warning(String message, [int charOffset = -1]) {
     messages.deprecated_warning(uri, charOffset, message);
   }
+
+  void warning(BoundFastaMessage bind, int charOffset) {
+    messages.warning(bind(uri, charOffset));
+  }
 }
 
 class Stack {