[DO NOT LAND] Set @@toStringTag for DOM object prototypes

Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp

Index: Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp
diff --git a/Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp b/Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp
index 3e0de777698a560254584ba8769230b8315dc3db..41ba9944cdd04033ceec4a6c5250f91577d65781 100644
--- a/Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp
+++ b/Source/bindings/tests/results/core/V8TestInterfaceDocument.cpp
@@ -44,6 +44,8 @@ static void installV8TestInterfaceDocumentTemplate(v8::Local<v8::FunctionTemplat
     v8::Local<v8::ObjectTemplate> prototypeTemplate = functionTemplate->PrototypeTemplate();
     ALLOW_UNUSED_LOCAL(prototypeTemplate);
 
+    prototypeTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterfaceDocument"));
+
     // Custom toString template
     functionTemplate->Set(v8AtomicString(isolate, "toString"), V8PerIsolateData::from(isolate)->toStringTemplate());
 }