Use FastaMessage instead of String. Part 1.

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

Index: pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart b/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
index 707aeda55fe272e4ef337aaace9ab9f92736192f..e585745ff767a4c63b54de006cd5696e7d3beef5 100644
--- a/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
@@ -13,7 +13,7 @@ import 'builder.dart'
         Scope,
         TypeBuilder;
 
-import '../messages.dart' show deprecated_warning;
+import '../messages.dart' show codeConstructorNotFound, warning;
 
 class ConstructorReferenceBuilder extends Builder {
   final String name;
@@ -58,8 +58,8 @@ class ConstructorReferenceBuilder extends Builder {
           suffix ?? "", charOffset, fileUri, accessingLibrary);
     }
     if (target == null) {
-      deprecated_warning(fileUri, charOffset,
-          "Couldn't find constructor '$fullNameForErrors'.");
+      warning(
+          codeConstructorNotFound.bind(fullNameForErrors)(fileUri, charOffset));
     }
   }
 }