Rollback to the older version of crypto to fix build.

pkg/analyzer/lib/src/summary/incremental_cache.dart

 // Copyright (c) 2016, 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:core' hide Resource;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 270 matching lines @@
     ChunkedConversionSink<Digest> digestSink =
         new ChunkedConversionSink<Digest>.withCallback((List<Digest> digests) {
       digest = digests.single;
     });
     ByteConversionSink byteSink = md5.startChunkedConversion(digestSink);
     // Add data.
     addData(byteSink);
     byteSink.add(configSalt);
     // Done.
     byteSink.close();
+
+    // TODO(paulberry): this call to `close` should not be needed.
+    // Can be removed once
+    //   https://github.com/dart-lang/crypto/issues/33
+    // is fixed – ensure the min version constraint on crypto is updated, tho.
+    // Does not cause any problems in the mean time.
+    digestSink.close();
+
     return digest.bytes;
   }
 
   /**
    * Return the [AnalysisError] for the given [cachedError].
    */
   AnalysisError _convertErrorFromCached(
       Source source, CacheAnalysisError cachedError) {
     ErrorCode errorCode = _getErrorCode(cachedError);
     return new AnalysisError.forValues(
@@ skipping 232 matching lines @@
    */
   final String id;
 
   /**
    * The payload bundle.
    */
   final PackageBundle bundle;
 
   LibraryBundleWithId(this.source, this.id, this.bundle);
 }