Implement HMAC support in lib/crypto.

tests/lib/test_config.dart

Index: tests/lib/test_config.dart
diff --git a/tests/lib/test_config.dart b/tests/lib/test_config.dart
index 4e9ef3e447845da486d1a4481477d208a7f6eab8..d9bb037c68012026e4d1ebf98c42b3cb8c7cfeec 100644
--- a/tests/lib/test_config.dart
+++ b/tests/lib/test_config.dart
@@ -11,7 +11,8 @@ class LibTestSuite extends StandardTestSuite {
       : super(configuration,
               "lib",
               "tests/lib/src",
-              ["tests/lib/lib.status"]);
+              ["tests/lib/lib.status"],
+              (s) => s.endsWith('_test.dart'));
 
   bool listRecursively() => true;
 }