[web snapshot] Improve error handling in Realm.useWebSnapshot()

Bug: v8:11525, v8:11706
Change-Id: Ia1f15ab33708831323bed5cdd9b8d3cf029cb7a1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2928183Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Vicky Kontoura <vkont@google.com>
Cr-Commit-Position: refs/heads/master@{#74863}

src/d8/d8.cc

@@ -1876,7 +1876,7 @@ void Shell::RealmTakeWebSnapshot(
 void Shell::RealmUseWebSnapshot(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   Isolate* isolate = args.GetIsolate();
-  if (args.Length() < 2) {
+  if (args.Length() < 2 || !args[1]->IsObject()) {
     isolate->ThrowError("Invalid argument");
     return;
   }
@@ -1885,7 +1885,8 @@ void Shell::RealmUseWebSnapshot(
   if (index == -1) return;
   // Restore the snapshot data from the snapshot object.
   Local<Object> snapshot_instance = args[1].As<Object>();
-  if (snapshot_instance->InternalFieldCount() != 1) {
+  Local<FunctionTemplate> snapshot_template = data->GetSnapshotObjectCtor();
+  if (!snapshot_template->HasInstance(snapshot_instance)) {
     isolate->ThrowError("Invalid argument");
     return;
   }