Make assertion scopes thread safe.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 9f52569ccf60fa1a03a7a6aafc178f991a22b6d6..683eacac2f7367599102a3d115516bd7bd7666cd 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3153,7 +3153,7 @@ class HConstant: public HTemplateInstruction<0> {
       // to be tenured so that it's guaranteed not be be located in new space.
       handle_ = FACTORY->NewNumber(double_value_, TENURED);
     }
-    ALLOW_HANDLE_DEREF(Isolate::Current(), "smi check");
+    ALLOW_DEFERRED_HANDLE_DEREF(Isolate::Current(), "smi check");
     ASSERT(has_int32_value_ || !handle_->IsSmi());
     return handle_;
   }