Parallel recompilation: fewer handle dereferences and tighter checks.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index fe1783d027ade4702804a51b7dda37bdc3f94bf1..2cbfd3b182ac978de156b8ef52b71f446506325b 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -6597,6 +6597,9 @@ bool Heap::SetUp() {
   store_buffer()->SetUp();
 
   if (FLAG_parallel_recompilation) relocation_mutex_ = OS::CreateMutex();
+#ifdef DEBUG
+  relocation_mutex_locked_ = false;
+#endif  // DEBUG
 
   return true;
 }