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

Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp

Index: Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp
diff --git a/Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp b/Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp
index 30cdfd88f8e745188b1a403cec65e79b3613f295..bae3b37d9a086c72e263789c79b2037db27dafda 100644
--- a/Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp
+++ b/Source/bindings/tests/results/core/V8TestInterfaceEventTarget.cpp
@@ -64,7 +64,7 @@ v8::Local<v8::FunctionTemplate> V8TestInterfaceEventTargetConstructor::domTempla
     result = v8::FunctionTemplate::New(isolate, V8TestInterfaceEventTargetConstructorCallback);
     v8::Local<v8::ObjectTemplate> instanceTemplate = result->InstanceTemplate();
     instanceTemplate->SetInternalFieldCount(V8TestInterfaceEventTarget::internalFieldCount);
-    result->SetClassName(v8AtomicString(isolate, "TestInterfaceEventTarget"));
+    instanceTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterfaceEventTarget"));
     result->Inherit(V8TestInterfaceEventTarget::domTemplate(isolate));
     data->setDOMTemplate(&domTemplateKey, result);
     return result;
@@ -84,6 +84,10 @@ static void installV8TestInterfaceEventTargetTemplate(v8::Local<v8::FunctionTemp
     v8::Local<v8::ObjectTemplate> prototypeTemplate = functionTemplate->PrototypeTemplate();
     ALLOW_UNUSED_LOCAL(prototypeTemplate);
 
+    instanceTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterfaceEventTarget"));
+
+    prototypeTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterfaceEventTargetPrototype"));
+
     // Custom toString template
     functionTemplate->Set(v8AtomicString(isolate, "toString"), V8PerIsolateData::from(isolate)->toStringTemplate());
 }