[dict-proto] Fix leaking handle in ExtractPropertyReferences

This fixes a handle leaking out of
V8HeapExplorer::ExtractPropertyReferences when enabling
v8_dict_mode_prototypes, which breaks the
test-heap-profiler/NoHandleLeaks cctest.

Bug: v8:11388
Change-Id: I911f60e3701277540ae5a63fa59f3ac2f52879ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2748580Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Frank Emrich <emrich@google.com>
Cr-Commit-Position: refs/heads/master@{#73319}

src/profiler/heap-snapshot-generator.cc

@@ -1378,6 +1378,10 @@ void V8HeapExplorer::ExtractPropertyReferences(JSObject js_obj,
       SetDataOrAccessorPropertyReference(details.kind(), entry, name, value);
     }
   } else if (V8_DICT_MODE_PROTOTYPES_BOOL) {
+    // SwissNameDictionary::IterateEntries creates a Handle, which should not
+    // leak out of here.
+    HandleScope scope(isolate);
+
     SwissNameDictionary dictionary = js_obj.property_dictionary_swiss();
     ReadOnlyRoots roots(isolate);
     for (InternalIndex i : dictionary.IterateEntries()) {