Add interfaces for a new compiler API.

tests/compiler/dart2js/message_kind_helper.dart

Index: tests/compiler/dart2js/message_kind_helper.dart
diff --git a/tests/compiler/dart2js/message_kind_helper.dart b/tests/compiler/dart2js/message_kind_helper.dart
index 7bc63ce886e2ac8c8f43aee22e330994993db919..244d5a0940d4d93691ce051511e79fd8e241ee83 100644
--- a/tests/compiler/dart2js/message_kind_helper.dart
+++ b/tests/compiler/dart2js/message_kind_helper.dart
@@ -12,6 +12,8 @@ import 'package:compiler/src/dart2jslib.dart' show
     MessageKind;
 import 'package:compiler/src/dart_backend/dart_backend.dart' show
     DartBackend;
+import 'package:compiler/src/old_to_new_api.dart' show
+    LegacyCompilerDiagnostics;
 
 import 'memory_compiler.dart';
 
@@ -79,7 +81,7 @@ Future<Compiler> check(MessageKind kind, Compiler cachedCompiler) {
 
     Compiler compiler = compilerFor(
         example,
-        diagnosticHandler: collect,
+        diagnosticHandler: new LegacyCompilerDiagnostics(collect),
         options: ['--analyze-only',
                   '--enable-experimental-mirrors']..addAll(kind.options),
         cachedCompiler: