protected ActiveMasterManager createActiveMasterManager(ZKWatcher zk, ServerName sn,
    org.apache.hadoop.hbase.Server server) throws InterruptedIOException {
    return new ActiveMasterManager(zk, sn, server);
  }
Protected to have custom implementations in tests override the default ActiveMaster
implementation.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java