@Override
    public void serialize(ByteBuffer destination, boolean includeNextBlockMetadata) {
      destination.putInt(buf.length);
      Thread.yield();
      destination.put(buf);
      destination.rewind();
    }
Just checks if heapsize grows when something is cached, and gets smaller when the same object
is evicted
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/CacheTestUtils.java