Follow-up to r25822: only internalize short strings optimistically

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 6b5d80c992d22517346caaf5e330426796275707..5d224d792eb2789ecb93aa1e4b9c5194a23668f6 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -17067,11 +17067,13 @@ Handle<HeapType> PropertyCell::UpdatedType(Handle<PropertyCell> cell,
 
 Handle<Object> PropertyCell::SetValueInferType(Handle<PropertyCell> cell,
                                                Handle<Object> value) {
-  // Heuristic: if a string is stored in a previously uninitialized
+  // Heuristic: if a small-ish string is stored in a previously uninitialized
   // property cell, internalize it.
+  const int kMaxLengthForInternalization = 200;
   if ((cell->type()->Is(HeapType::None()) ||
        cell->type()->Is(HeapType::Undefined())) &&
-      value->IsString()) {
+      value->IsString() &&
+      Handle<String>::cast(value)->length() <= kMaxLengthForInternalization) {
     value = cell->GetIsolate()->factory()->InternalizeString(
         Handle<String>::cast(value));
   }