Close underlying Hash sinks.

test/sha1_test.dart

Index: test/sha1_test.dart
diff --git a/test/sha1_test.dart b/test/sha1_test.dart
index 5b7398b2bf4bf286e2d8793643f4b5e036625d84..3b629b0373c8fa41d52172baf8d5ffcd6f3b2636 100644
--- a/test/sha1_test.dart
+++ b/test/sha1_test.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import "dart:async";
+import "dart:convert";
 
 import "package:crypto/crypto.dart";
 import "package:test/test.dart";
@@ -24,6 +25,18 @@ void main() {
       sink.close();
       sink.close();
     });
+
+    test('close closes the underlying sink', () {
+      var inner = new ChunkedConversionSink<Digest>.withCallback(
+          expectAsync((accumulated) {
+        expect(accumulated.length, equals(1));
+        expect(accumulated.first.toString(),
+            equals("da39a3ee5e6b4b0d3255bfef95601890afd80709"));
+      }));
+
+      var outer = sha1.startChunkedConversion(inner);
+      outer.close();
+    });
   });
 
   group("standard vector", () {