test large inputs for sha1 and sha256, also remove unused import

lib/src/hash_base.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.
 
 library crypto.hash_base;
 
-import 'dart:math' as math;
 import 'dart:typed_data';
 
 import 'hash.dart';
 import 'utils.dart';
 
 /// A base class for [Hash] implementations.
 ///
 /// Subclasses should override [updateHash], and define it to update [h] with
 /// the results of the hash function.
 abstract class HashBase implements Hash {
@@ skipping 149 matching lines @@
       _pendingData.addAll(_wordToBytes(lengthInBits & MASK_32));
     } else {
       _pendingData.addAll(_wordToBytes(lengthInBits & MASK_32));
       _pendingData.addAll(_wordToBytes((lengthInBits >> 32) & MASK_32));
     }
   }
 
   /// Rounds [val] to the nearest multiple of [n].
   int _roundUp(val, n) => (val + n - 1) & -n;
 }