@edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "MS_EXPOSE_REP",
      justification = "singleton pattern")
  public static ChunkCreator getInstance() {
    return instance;
  }
Initializes the instance of ChunkCreator
@param chunkSize              the chunkSize
@param offheap                indicates if the chunk is to be created offheap or not
@param globalMemStoreSize     the global memstore size
@param poolSizePercentage     pool size percentage
@param initialCountPercentage the initial count of the chunk pool if any
@param heapMemoryManager      the heapmemory manager
@return singleton MSLABChunkCreator
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ChunkCreator.java