Optimize functions on a second thread.

test/cctest/test-mark-compact.cc

Index: test/cctest/test-mark-compact.cc
diff --git a/test/cctest/test-mark-compact.cc b/test/cctest/test-mark-compact.cc
index 27123704b12ddcff5bd6d745ef851ab512ee6bfb..f09a3ce42fca3bc88fc98d29641ef638d7a9541b 100644
--- a/test/cctest/test-mark-compact.cc
+++ b/test/cctest/test-mark-compact.cc
@@ -526,7 +526,10 @@ static intptr_t MemoryInUse() {
 
 TEST(BootUpMemoryUse) {
   intptr_t initial_memory = MemoryInUse();
-  FLAG_crankshaft = false;  // Avoid flakiness.
+  // Avoid flakiness.
+  FLAG_crankshaft = false;
+  FLAG_parallel_recompilation = false;
+
   // Only Linux has the proc filesystem and only if it is mapped.  If it's not
   // there we just skip the test.
   if (initial_memory >= 0) {