Limit the number of transitions allowed per hidden class.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 5d85b13614ca6c2c64592cf769e2b7a88d5a5936..5473e690eb2a852b34f2269bdf1c3b563d7cfb62 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -6594,7 +6594,8 @@ Handle<Map> Map::ShareDescriptor(Handle<Map> map,
     if (old_size == 0) {
       descriptors = DescriptorArray::Allocate(map->GetIsolate(), 0, 1);
     } else {
-      EnsureDescriptorSlack(map, old_size < 4 ? 1 : old_size / 2);
+      EnsureDescriptorSlack(
+          map, SlackForArraySize(old_size, kMaxNumberOfDescriptors));
       descriptors = handle(map->instance_descriptors());
     }
   }
@@ -6619,8 +6620,11 @@ void Map::ConnectTransition(Handle<Map> parent, Handle<Map> child,
     DCHECK(child->is_prototype_map());
   } else {
     Handle<TransitionArray> transitions =
-        TransitionArray::CopyInsert(parent, name, child, flag);
-    parent->set_transitions(*transitions);
+        TransitionArray::Insert(parent, name, child, flag);
+    if (!parent->HasTransitionArray() ||
+        *transitions != parent->transitions()) {
+      parent->set_transitions(*transitions);
+    }
     child->SetBackPointer(*parent);
   }
 }