anchor.diff:  import 'package:analyzer/src/summary/summarize_elements.dart';
   import 'package:convert/convert.dart';
   import 'package:crypto/crypto.dart';
  +
  +/**
  + * The version of the incremental cache.  It should be incremented every time
  + * when any cache data structure is changed.
  + */
  +const int _VERSION = 1;
   
   /**
    * Storage for cache data.
  
positive.code:     ByteConversionSink byteSink = md5.startChunkedConversion(digestSink);
      // Add data.
      addData(byteSink);
      byteSink.add(configSalt);
      // Done.
      byteSink.close();
  
negative.code:         return null;
        }
        bundle = new PackageBundle.fromBuffer(bytes);
        if (bundle.majorVersion != PackageBundleAssembler.currentMajorVersion ||
            bundle.minorVersion != PackageBundleAssembler.currentMinorVersion) {
          return null;
        }
        _bundleMap[key] = bundle;
      }
      return bundle;
  