@Override
            public void run() {
                if (callback != null) {
                    callback.onDone(message);
                    if (idlingResource != null) {
                        idlingResource.setIdleState(true);
                    }
                }
            }
Takes a String and returns it after {@link #DELAY_MILLIS} via a {@link DelayerCallback}.
@param message the String that will be returned via the callback
@param callback used to notify the caller asynchronously
ui/espresso/IdlingResourceSample/app/src/main/java/com/example/android/testing/espresso/IdlingResourceSample/MessageDelayer.java