Use same code on heap buffers and direct buffers.
Snippet of current code:
        protected CoderResult decodeLoop(ByteBuffer src,
                                         CharBuffer dst)
        {
            if (src.hasArray() && dst.hasArray())
                return decodeArrayLoop(src, dst);
            else
                return decodeBufferLoop(src, dst);
        }

Since access to heap buffers and direct buffers is now optimized via Unsafe [1], there is no more need to separately optimize the code for heap buffers and direct buffers.
[1] https://bugs.openjdk.java.net/browse/JDK-8149469