[serializer] Disable gc-stats during deserialisation

Objects might be in a partially initialized state during deserialization
which makes collecting gc-stats tricky.

Bug: v8:12678
Change-Id: I154328adda432bf8e3588c96455c1bd8d527ef43
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3635722Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80446}

src/snapshot/deserializer.h

@@ -254,6 +254,25 @@ class Deserializer : public SerializerDeserializer {
   const bool should_rehash_;
   std::vector<Handle<HeapObject>> to_rehash_;
 
+  // Do not collect any gc stats during deserialization since objects might
+  // be in an invalid state
+  class V8_NODISCARD DisableGCStats {
+   public:
+    explicit DisableGCStats() {
+      if (V8_LIKELY(!TracingFlags::is_gc_stats_enabled())) return;
+      was_enabled_ = true;
+      TracingFlags::gc_stats = false;
+    }
+    ~DisableGCStats() {
+      if (V8_LIKELY(!was_enabled_)) return;
+      TracingFlags::gc_stats = true;
+    }
+
+   private:
+    bool was_enabled_ = false;
+  };
+  DisableGCStats no_gc_stats_;
+
 #ifdef DEBUG
   uint32_t num_api_references_;