code: @Trivial // traced by caller
      static <U> CompletableFuture<U> completedFuture(U value, Executor executor) {
          if (JAVA8) {
              return new ManagedCompletableFuture<U>(CompletableFuture.completedFuture(value), executor, null);
          } else {
              ManagedCompletableFuture<U> future = new ManagedCompletableFuture<U>(executor, null);
              future.super_complete(value);
              return future;
          }
      }
docs: Provides the implementation of managedExecutor.completedFuture(value) where the target
  executor is the default asynchronous execution facility.
  
  @param value result of the completed future
  @param executor executor to become the default asynchronous execution facility for the completed future
  @return completed completable future