During the review for JDK-8195716 a number of suggestions to improve the BootstrapLoggerTest were made:

1. Martin Buchholz suggested copying the logic of gcAwait from a concurrency test, e.g.:
    ArrayBlockingQueue/WhiteBox.java:229: static void gcAwait(BooleanSupplier s) {

2. Mandy Chung suggested adding more whitebox test hooks, like a
    method to join the executor's threads. That should simplify the
   logic in the test.