Parallel recompilation: fewer handle dereferences and tighter checks.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 456e9d87a99871ade907de6656f8881d9f9792b5..b54b83a275cb64aed1b1b5f6c92f8f3e230832bb 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1822,14 +1822,27 @@ class Heap {
     explicit RelocationLock(Heap* heap) : heap_(heap) {
       if (FLAG_parallel_recompilation) {
         heap_->relocation_mutex_->Lock();
+#ifdef DEBUG
+        heap_->relocation_mutex_locked_ = true;
+#endif  // DEBUG
       }
     }
+
     ~RelocationLock() {
       if (FLAG_parallel_recompilation) {
+#ifdef DEBUG
+        heap_->relocation_mutex_locked_ = false;
+#endif  // DEBUG
         heap_->relocation_mutex_->Unlock();
       }
     }
 
+#ifdef DEBUG
+    static bool IsLocked(Heap* heap) {
+      return heap->relocation_mutex_locked_;
+    }
+#endif  // DEBUG
+
    private:
     Heap* heap_;
   };
@@ -2304,6 +2317,9 @@ class Heap {
   MemoryChunk* chunks_queued_for_free_;
 
   Mutex* relocation_mutex_;
+#ifdef DEBUG
+  bool relocation_mutex_locked_;
+#endif  // DEBUG;
 
   friend class Factory;
   friend class GCTracer;