Run Crankshaft on a separate thread.

test/cctest/test-debug.cc

Index: test/cctest/test-debug.cc
diff --git a/test/cctest/test-debug.cc b/test/cctest/test-debug.cc
index e40f406c3c5f869743cb13e2f0d75b4afb95b480..cc68df7dc1c7a63127ccfad98c83ea517b126133 100644
--- a/test/cctest/test-debug.cc
+++ b/test/cctest/test-debug.cc
@@ -461,10 +461,17 @@ void ForceUnloadDebugger() {
 
 // Check that the debugger has been fully unloaded.
 static void CheckDebuggerUnloaded(bool check_functions = false) {
-  // Let debugger to unload itself synchronously
-  v8::Debug::ProcessDebugMessages();
+  if (i::FLAG_optimize_in_parallel) {
+    v8::HandleScope scope;
 
-  v8::internal::CheckDebuggerUnloaded(check_functions);
+    // Let debugger to unload itself synchronously
+    v8::Debug::ProcessDebugMessages();
+    v8::internal::CheckDebuggerUnloaded(check_functions);
+  } else {
+    // Let debugger to unload itself synchronously
+    v8::Debug::ProcessDebugMessages();
+    v8::internal::CheckDebuggerUnloaded(check_functions);
+  }
 }