worked everywhere that I know of except for one place: when running the GWT
    util.concurrent tests under Guava.

    The problem is that GWT responds poorly to two .gwt.xml files in the same
    Java package; see https://goo.gl/pRV3Yn for details.

    The summary is that it ignores one file in favor of the other.
    util.concurrent, like nearly all our packages, has two .gwt.xml files: one

concurrent-burgers-02.png...

concurrent-burgers-04.png...

concurrent-burgers-01.png...

concurrent-burgers-03.png...

concurrent-burgers-05.png...

concurrent-burgers-06.png...

concurrent-burgers-07.png...

import com.google.common.annotations.GwtIncompatible;
import java.time.Duration;
import java.util.EnumSet;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**

 */

package com.google.common.util.concurrent;

import static com.google.common.util.concurrent.Futures.getUnchecked;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.CHECKED_EXCEPTION;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.ERROR;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.ERROR_FUTURE;