@Override
		public Thread newThread(Runnable r) {
			assert threadNumber < NUMBER_OF_THREADS;
			return new NumberedThread(r, threadNumber);
		}
This method is separate from {@link #parse1} so the first pass can be distinguished when analyzing
 profiler results.
tool-testsuite/test/org/antlr/v4/test/tool/TestPerformance.java