Roll to pickup pool changes

packages/crypto/lib/src/hmac.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:convert';
 import 'dart:typed_data';
 
 import 'digest.dart';
 import 'digest_sink.dart';
 import 'hash.dart';
@@ skipping 67 matching lines @@
 
     // Compute inner padding.
     for (var i = 0; i < padding.length; i++) {
       padding[i] = 0x36 ^ key[i];
     }
     _innerSink.add(padding);
   }
 
   @override
   void add(List<int> data) {
-    if (_isClosed) throw new StateError("HMAC is closed");
+    if (_isClosed) throw new StateError('HMAC is closed');
     _innerSink.add(data);
   }
 
   @override
   void addSlice(List<int> data, int start, int end, bool isLast) {
-    if (_isClosed) throw new StateError("HMAC is closed");
+    if (_isClosed) throw new StateError('HMAC is closed');
     _innerSink.addSlice(data, start, end, isLast);
   }
 
   @override
   void close() {
     if (_isClosed) return;
     _isClosed = true;
 
     _innerSink.close();
     _outerSink.add(_innerResultSink.value.bytes);
     _outerSink.close();
   }
 }