Remove dart backend

test/dart_codegen/types/a.dart

Index: test/dart_codegen/types/a.dart
diff --git a/test/dart_codegen/types/a.dart b/test/dart_codegen/types/a.dart
deleted file mode 100644
index 8070d6cdaa7e95cb6eee2866ed4291bc14e915f7..0000000000000000000000000000000000000000
--- a/test/dart_codegen/types/a.dart
+++ /dev/null
@@ -1,10 +0,0 @@
-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library a;
-
-class A {}
-
-typedef A A2A(A x);
-typedef dynamic D2D(dynamic x);