protected ByteBuffer mergeResponseBuffer(ByteBuffer buffer) {
        return merge(mResponsePendingBuffers, buffer);
    }
Merge all the response pending buffers and a given buffer, and output a new buffer which
contains all data. The pending buffers will be clear after the merge action.

@param buffer A fresh packet buffer.
@return A new buffer.
netbare-core/src/main/java/com/github/megatronking/netbare/gateway/PendingIndexedInterceptor.java