static ByteBuf expandCumulation(ByteBufAllocator alloc, ByteBuf cumulation, int readable) {
        ByteBuf oldCumulation = cumulation;
        cumulation = alloc.buffer(oldCumulation.readableBytes() + readable);
        cumulation.writeBytes(oldCumulation);
        oldCumulation.release();
        return cumulation;
    }
Is called one last time when the {@link ChannelHandlerContext} goes in-active. Which means the
{@link #channelInactive(ChannelHandlerContext)} was triggered.

By default this will just call {@link #decode(ChannelHandlerContext, ByteBuf, List)} but sub-classes may
override this for some special cleanup operation.
src/main/java/com/alipay/remoting/codec/AbstractBatchDecoder.java