Use FastaMessage instead of String. Part 1.

pkg/front_end/lib/src/fasta/builder/class_builder.dart

Index: pkg/front_end/lib/src/fasta/builder/class_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/class_builder.dart b/pkg/front_end/lib/src/fasta/builder/class_builder.dart
index 07a9b2e47736254a099e0cd3dffcbeaab8e16c21..7e64fda6e281f2c2fcd570e8c0d5e979f87c2e79 100644
--- a/pkg/front_end/lib/src/fasta/builder/class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/class_builder.dart
@@ -21,6 +21,8 @@ import 'builder.dart'
         TypeDeclarationBuilder,
         TypeVariableBuilder;
 
+import '../fasta_codes.dart' show Message;
+
 abstract class ClassBuilder<T extends TypeBuilder, R>
     extends TypeDeclarationBuilder<T, R> {
   final List<TypeVariableBuilder> typeVariables;
@@ -198,6 +200,18 @@ abstract class ClassBuilder<T extends TypeBuilder, R>
         deprecated_internalProblem("Not found: '$name'.");
   }
 
+  void addCompileTimeError(Message message, int charOffset) {
+    library.addCompileTimeError(message, charOffset, fileUri);
+  }
+
+  void addWarning(Message message, int charOffset) {
+    library.addWarning(message, charOffset, fileUri);
+  }
+
+  void addNit(Message message, int charOffset) {
+    library.addNit(message, charOffset, fileUri);
+  }
+
   void deprecated_addCompileTimeError(int charOffset, String message) {
     library.deprecated_addCompileTimeError(charOffset, message,
         fileUri: fileUri);