Fix wrintInt64 for CodedBufferWriter
Fix wrintInt64 for CodedBufferWriter

dart-lang/dart-protobuf,google/protobuf.dart,dart-lang/dart-protobuf,dart-lang/protobuf,dart-lang/protobuf,google/protobuf.dart,dart-lang/dart-protobuf,google/protobuf.dart,dart-lang/protobuf