Build ScopeInfo in the right order for web snapshots

Currently, WebSnapshotDeserializer::CreateScopeInfo creates the
ScopeInfo first, and then creates its local names hashtable if
necessary. If GC occurs when creating the local names hashtable, the
object verifier correctly complains that the ScopeInfo doesn't have all
needed fields. The solution (consistent with ScopeInfo::Create) is to
create the local names hashtable first. That way, no GC can happen in
the interval after the ScopeInfo is allocated but before it has valid
fields.

Bug: v8:13135
Change-Id: Ifd6eb10e54a4151f7edb592bc19afa3263d41788
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3803674Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82155}

src/web-snapshot/web-snapshot.cc

@@ -2661,8 +2661,12 @@ Handle<ScopeInfo> WebSnapshotDeserializer::CreateScopeInfo(
                           : 0) +
                      (has_parent ? 1 : 0) + local_names_container_size +
                      variable_count;
-  Handle<ScopeInfo> scope_info = factory()->NewScopeInfo(length);
   Handle<NameToIndexHashTable> local_names_hashtable;
+  if (!has_inlined_local_names) {
+    local_names_hashtable = NameToIndexHashTable::New(isolate_, variable_count,
+                                                      AllocationType::kOld);
+  }
+  Handle<ScopeInfo> scope_info = factory()->NewScopeInfo(length);
   {
     DisallowGarbageCollection no_gc;
     ScopeInfo raw = *scope_info;
@@ -2676,11 +2680,9 @@ Handle<ScopeInfo> WebSnapshotDeserializer::CreateScopeInfo(
     if (raw.HasPositionInfo()) {
       raw.SetPositionInfo(0, 0);
     }
-  }
-  if (!has_inlined_local_names) {
-    local_names_hashtable = NameToIndexHashTable::New(isolate_, variable_count,
-                                                      AllocationType::kOld);
-    scope_info->set_context_local_names_hashtable(*local_names_hashtable);
+    if (!has_inlined_local_names) {
+      raw.set_context_local_names_hashtable(*local_names_hashtable);
+    }
   }
   return scope_info;
 }