binding: Updates a comment of the class string on the platform objects.

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 597 matching lines @@
     const char* interfaceName,
     v8::Local<v8::FunctionTemplate> parentInterfaceTemplate,
     size_t v8InternalFieldCount) {
   interfaceTemplate->SetClassName(v8AtomicString(isolate, interfaceName));
   interfaceTemplate->ReadOnlyPrototype();
   v8::Local<v8::ObjectTemplate> instanceTemplate =
       interfaceTemplate->InstanceTemplate();
   v8::Local<v8::ObjectTemplate> prototypeTemplate =
       interfaceTemplate->PrototypeTemplate();
   instanceTemplate->SetInternalFieldCount(v8InternalFieldCount);
-  // TODO(yukishiino): We should set the class string to the platform object
-  // (|instanceTemplate|), too.  The reason that we don't set it is that
-  // 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
+
+  // We intentionally don't set the class string to the platform object
+  // (|instanceTemplate|), and set the class string "InterfaceName", without
+  // "Prototype", to the prototype object (|prototypeTemplate|) despite a fact
+  // that the current WebIDL spec (as of Feb 2017) requires to set the class
+  // string "InterfaceName" for the platform objects and
+  // "InterfaceNamePrototype" for the interface prototype object, because we
+  // think it's more consistent with ECMAScript 2016.
+  // See also https://crbug.com/643712
+  // https://heycam.github.io/webidl/#es-platform-objects
+  // https://heycam.github.io/webidl/#interface-prototype-object
+  //
+  // Note that V8 minor GC does not collect an object which has an own property.
+  // So, if we set the class string to the platform object as an own property,
+  // it prevents V8 minor GC to collect the object (V8 minor GC only collects
+  // an empty object).  If set, a layout test fast/dom/minor-dom-gc.html fails.
   setClassString(isolate, prototypeTemplate, interfaceName);
+
   if (!parentInterfaceTemplate.IsEmpty()) {
     interfaceTemplate->Inherit(parentInterfaceTemplate);
     // 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);
   }
 }
 
@@ skipping 18 matching lines @@
 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