Keep prototype maps in dictionary mode until ICs see them

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index cb787374c81378898ba0f13c204776fa6b719eae..36a2e0097d34412a18b379a57fbd8aea50ffae95 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4576,6 +4576,10 @@ bool Map::is_prototype_map() const {
   return IsPrototypeMapBits::decode(bit_field2());
 }
 
+bool Map::should_be_fast_prototype_map() const {
+  if (!prototype_info()->IsPrototypeInfo()) return false;
+  return PrototypeInfo::cast(prototype_info())->should_be_fast_map();
+}
 
 void Map::set_elements_kind(ElementsKind elements_kind) {
   DCHECK(static_cast<int>(elements_kind) < kElementsKindCount);
@@ -5511,6 +5515,8 @@ ACCESSORS(Box, value, Object, kValueOffset)
 ACCESSORS(PrototypeInfo, prototype_users, Object, kPrototypeUsersOffset)
 SMI_ACCESSORS(PrototypeInfo, registry_slot, kRegistrySlotOffset)
 ACCESSORS(PrototypeInfo, validity_cell, Object, kValidityCellOffset)
+SMI_ACCESSORS(PrototypeInfo, bit_field, kBitFieldOffset)
+BOOL_ACCESSORS(PrototypeInfo, bit_field, should_be_fast_map, kShouldBeFastBit)
 
 ACCESSORS(SloppyBlockWithEvalContextExtension, scope_info, ScopeInfo,
           kScopeInfoOffset)