anchor.diff:            nullability,
             expectedLength);
   
  +  static const _utf8Decoder = const Utf8Decoder();
  +
     String decodeString(int offset, bool nullable) {
       int nullability = nullable ? kArrayNullable : 0;
       var bytes = decodeUint8Array(offset, nullability, kUnspecifiedArrayLength);
       if (bytes == null) {
         return null;
       }
  -    return (const Utf8Decoder()).convert(bytes);
  +    return _utf8Decoder.convert(bytes);
     }
   
     StructDataHeader decodeDataHeaderForMap() {
  
positive.code:   // Decode arrays.
    ArrayDataHeader decodeDataHeaderForBoolArray(int expectedLength) {
      var header = decodeArrayDataHeader();
      var arrayByteCount =
          ArrayDataHeader.kHeaderSize + (header.numElements + 7) ~/ 8;
      if (header.size < arrayByteCount) {
        throw new MojoCodecError('Array header is incorrect');
      }
  
negative.code:     extent += claimSize;
      if (extent > buffer.lengthInBytes) {
        int newSize = buffer.lengthInBytes + claimSize;
        newSize += (newSize >> 1);
        _grow(newSize);
      }
    }
  