@Override
      public int getSerializedLength() {
        return (int) heapSize();
      }
Assert that when BUCKET_CACHE_COMBINED_KEY is false, the non-default, that we deploy
LruBlockCache as L1 with a BucketCache for L2.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestCacheConfig.java