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 598 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|), because we

[Matt Giuca, 2017/02/05 23:18:08]

It seems a bit strange out of context to be saying "without "Prototype""... why
would there be an expectation of it having "Prototype" at the end?

Perhaps add "(as required by the current WebIDL draft, as of February 2017)" or
something, to say basically this comment marks an explicit deviation from the
draft standard.

[Yuki, 2017/02/14 12:58:46]

Done.

+  // think it's more consistent with ECMAScript 2016.
+  // See also https://crbug.com/643712
+  //
+  // 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