@Override
    public void add(O out) {
        if (tryWrite(out)) {
            handlerProduced = true;
        } else {
            cancelAndCleanup();
        }
    }
Returns a new {@link DecodedStreamMessage} with the specified {@link HttpDecoder},
{@link ByteBufAllocator} and {@code byteBufConverter}.
core/src/main/java/com/linecorp/armeria/internal/common/stream/DecodedStreamMessage.java