[heap] #ifdef FLAG_minor_mc use

This is the only FLAG_minor_mc usage that is not guarded by
#ifdef ENABLE_MINOR_MC.

Change-Id: I54d447ede6a6ab4bbfb6ffbd7674e240d8cc1987
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2260878Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68494}

src/heap/heap.cc

@@ -4320,9 +4320,9 @@ class OldToNewSlotVerifyingVisitor : public SlotVerifyingVisitor {
   void VisitEphemeron(HeapObject host, int index, ObjectSlot key,
                       ObjectSlot target) override {
     VisitPointer(host, target);
-    if (FLAG_minor_mc) {
-      VisitPointer(host, target);
-    } else {
+#ifdef ENABLE_MINOR_MC
+    if (FLAG_minor_mc) return VisitPointer(host, target);
+#endif
     // Keys are handled separately and should never appear in this set.
     CHECK(!InUntypedSet(key));
     Object k = *key;
@@ -4336,7 +4336,6 @@ class OldToNewSlotVerifyingVisitor : public SlotVerifyingVisitor {
       CHECK(it->second.find(entry.as_int()) != it->second.end());
     }
   }
-  }
 
  private:
   EphemeronRememberedSet* ephemeron_remembered_set_;