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

Source/bindings/tests/results/core/V8TestInterface3.cpp

Index: Source/bindings/tests/results/core/V8TestInterface3.cpp
diff --git a/Source/bindings/tests/results/core/V8TestInterface3.cpp b/Source/bindings/tests/results/core/V8TestInterface3.cpp
index e7e80fc340fa42ac8f7a1faeb9f5574b94d49955..465c3e162c14c230433173ece61782f6047dd6df 100644
--- a/Source/bindings/tests/results/core/V8TestInterface3.cpp
+++ b/Source/bindings/tests/results/core/V8TestInterface3.cpp
@@ -324,6 +324,10 @@ static void installV8TestInterface3Template(v8::Local<v8::FunctionTemplate> func
         V8DOMConfiguration::installMethod(isolate, prototypeTemplate, defaultSignature, v8::None, forEachMethodConfiguration);
     }
 
+    instanceTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterface3"));
+
+    prototypeTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, "TestInterface3Prototype"));
+
     // Custom toString template
     functionTemplate->Set(v8AtomicString(isolate, "toString"), V8PerIsolateData::from(isolate)->toStringTemplate());
 }