Fix issues when changing FLAG_concurrent_recompilation after init.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index f6cd3ebe5454fc18245f6e34a07920d62fd908a6..931972baeb5ed0857770cb6d656ac1d0a92dd2a1 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1906,16 +1906,12 @@ class Heap {
   class RelocationLock {
    public:
     explicit RelocationLock(Heap* heap) : heap_(heap) {
-      if (FLAG_concurrent_recompilation) {
-        heap_->relocation_mutex_->Lock();
-      }
+      heap_->relocation_mutex_.Lock();
     }
 
 
     ~RelocationLock() {
-      if (FLAG_concurrent_recompilation) {
-        heap_->relocation_mutex_->Unlock();
-      }
+      heap_->relocation_mutex_.Unlock();
     }
 
    private:
@@ -2518,7 +2514,7 @@ class Heap {
 
   MemoryChunk* chunks_queued_for_free_;
 
-  Mutex* relocation_mutex_;
+  Mutex relocation_mutex_;
 
   int gc_callbacks_depth_;