private void setOldestEditTimeToNow() {
    if (timeOfOldestEdit == Long.MAX_VALUE) {
      timeOfOldestEdit = EnvironmentEdgeManager.currentTime();
    }
  }
Internal version of add() that doesn't clone Cells with the allocator, and doesn't take the
lock. Callers should ensure they already have the read lock taken
@param toAdd          the cell to add
@param mslabUsed      whether using MSLAB
@param memstoreSizing object to accumulate changed size
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/AbstractMemStore.java