Supports "class string" based on @@toStringTag.

third_party/WebKit/Source/bindings/core/v8/V8DOMConfiguration.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 295 matching lines @@
 
 v8::Local<v8::Signature> V8DOMConfiguration::installDOMClassTemplate(v8::Isolate* isolate, v8::Local<v8::FunctionTemplate> functionDescriptor, const char* interfaceName, v8::Local<v8::FunctionTemplate> parentClass, size_t fieldCount,
     const AttributeConfiguration* attributes, size_t attributeCount,
     const AccessorConfiguration* accessors, size_t accessorCount,
     const MethodConfiguration* methods, size_t methodCount)
 {
     functionDescriptor->SetClassName(v8AtomicString(isolate, interfaceName));
     v8::Local<v8::ObjectTemplate> instanceTemplate = functionDescriptor->InstanceTemplate();
     v8::Local<v8::ObjectTemplate> prototypeTemplate = functionDescriptor->PrototypeTemplate();
     instanceTemplate->SetInternalFieldCount(fieldCount);
+    // TODO(yukishiino): We should set the class string to the platform object
+    // (|instanceTemplate|), too.  The reason that we don't set it is that

[adamk, 2016/02/12 18:31:33]

Can you say more about exactly what this patch does in the CL description? It
refers to the WebIDL spec, but since you're not setting the property on the
instances, we don't match the spec directly. See the bug caitp links to for more
discussion of the issues at hand; there's more at stake than just the
minor-dom-gc layout test.

+    // it prevents minor GC to collect unreachable DOM objects (a layout test
+    // fast/dom/minor-dom-gc.html fails if we set the class string).
+    // See also http://heycam.github.io/webidl/#es-platform-objects

[caitp (gmail), 2016/02/12 14:44:46]

Has there been more discussion about this since
https://www.w3.org/Bugs/Public/show_bug.cgi?id=28244 ?

+    setClassString(isolate, prototypeTemplate, interfaceName);
     if (!parentClass.IsEmpty()) {
         functionDescriptor->Inherit(parentClass);
         // Marks the prototype object as one of native-backed objects.
         // This is needed since bug 110436 asks WebKit to tell native-initiated prototypes from pure-JS ones.
         // This doesn't mark kinds "root" classes like Node, where setting this changes prototype chain structure.
         prototypeTemplate->SetInternalFieldCount(v8PrototypeInternalFieldcount);
     }
 
     v8::Local<v8::Signature> defaultSignature = v8::Signature::New(isolate, functionDescriptor);
     if (attributeCount)
@@ skipping 12 matching lines @@
     if (!result.IsEmpty())
         return result;
 
     TRACE_EVENT_SCOPED_SAMPLING_STATE("blink", "BuildDOMTemplate");
     result = v8::FunctionTemplate::New(isolate, V8ObjectConstructor::isValidConstructorMode);
     configureDOMClassTemplate(result, isolate);
     data->setDOMTemplate(wrapperTypeInfo, result);
     return result;
 }
 
+void V8DOMConfiguration::setClassString(v8::Isolate* isolate, v8::Local<v8::ObjectTemplate> objectTemplate, const char* classString)
+{
+    objectTemplate->Set(v8::Symbol::GetToStringTag(isolate), v8AtomicString(isolate, classString), static_cast<v8::PropertyAttribute>(v8::ReadOnly | v8::DontEnum));
+}
+
 } // namespace blink