[runtime] Weaken a DCHECK

It can happen that the {value} handle initially (when we stored its
contents into the property cell) contained a ThinString but was
subsequently patched by the scavenger to hold the InternalizedString
directly.

Bug: v8:11675
Change-Id: Ia3e5fed5bd28313b6fd2031eee0658ac4136a7ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2843350Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74083}

src/objects/lookup.cc

@@ -1031,7 +1031,9 @@ void LookupIterator::WriteDataValue(Handle<Object> value,
     GlobalDictionary dictionary =
         JSGlobalObject::cast(*holder).global_dictionary(isolate_, kAcquireLoad);
     PropertyCell cell = dictionary.CellAt(isolate_, dictionary_entry());
-    DCHECK_EQ(cell.value(), *value);
+    DCHECK(cell.value() == *value ||
+           cell.value().IsString() && value->IsString() &&
+               String::cast(cell.value()).Equals(String::cast(*value)));
 #endif  // DEBUG
   } else {
     DCHECK_IMPLIES(holder->IsJSProxy(isolate_), name()->IsPrivate(isolate_));