[runtime] Recreate enum cache on map update

If we had one before, we probably want one after too.

Bug: chromium:1470668
Change-Id: Ib83f7b9549b5686a16d35dd7114bf88b12d0a3a0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4771019
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#89488}

src/objects/map-updater.cc

@@ -12,6 +12,7 @@
 #include "src/handles/handles.h"
 #include "src/heap/parked-scope-inl.h"
 #include "src/objects/field-type.h"
+#include "src/objects/keys.h"
 #include "src/objects/objects-inl.h"
 #include "src/objects/objects.h"
 #include "src/objects/property-details.h"
@@ -1038,6 +1039,12 @@ MapUpdater::State MapUpdater::ConstructNewMap() {
   // the new descriptors to maintain descriptors sharing invariant.
   split_map->ReplaceDescriptors(isolate_, *new_descriptors);
 
+  // If the old descriptors had an enum cache, make sure the new ones do too.
+  if (old_descriptors_->enum_cache()->keys()->length() > 0) {
+    FastKeyAccumulator::InitializeFastPropertyEnumCache(
+        isolate_, new_map, new_map->NumberOfEnumerableProperties());
+  }
+
   if (has_integrity_level_transition_) {
     target_map_ = new_map;
     state_ = kAtIntegrityLevelSource;