* newFuture is a future that completes after this and all prior tasks are done.
     * oldFuture is the previous task's newFuture.
     * outputFuture is the future we return to the caller, a nonCancellationPropagating taskFuture.
     *
     * newFuture is guaranteed to only complete once all tasks previously submitted to this instance
     * have completed - namely after oldFuture is done, and taskFuture has either completed or been

     * newFuture is a future that completes after this and all prior tasks are done.
     * oldFuture is the previous task's newFuture.
     * outputFuture is the future we return to the caller, a nonCancellationPropagating taskFuture.
     *
     * newFuture is guaranteed to only complete once all tasks previously submitted to this instance
     * have completed - namely after oldFuture is done, and taskFuture has either completed or been

import static com.google.common.util.concurrent.Futures.getDone;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.Futures.nonCancellationPropagating;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.Platform.restoreInterruptIfIsInterruptedException;
import static java.util.logging.Level.FINER;