code: public UBench addDoubleTask(String name, DoubleSupplier task) {
          return addDoubleTask(name, task, null);
      }
docs: Include a double-specialized named task in to the benchmark.
  
  @param name
  The name of the task. Only one task with any one name is
  allowed.
  @param task
  The task to perform
  @return The same object, for chaining calls.