Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/bindings/core/v8/ScriptWrappable.h

 /*
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ScriptWrappable_h
 #define ScriptWrappable_h
 
 #include "bindings/core/v8/WrapperTypeInfo.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/TypeTraits.h"
 #include <v8.h>
 
 namespace blink {
 
 /**
  * ScriptWrappable wraps a V8 object and its WrapperTypeInfo.
  *
  * ScriptWrappable acts much like a v8::Persistent<> in that it keeps a
  * V8 object alive.
  *
  *  The state transitions are:
  *  - new: an empty ScriptWrappable.
  *  - setWrapper: install a v8::Persistent (or empty)
  *  - disposeWrapper (via setWeakCallback, triggered by V8 garbage collecter):
  *        remove v8::Persistent and become empty.
  */
 class CORE_EXPORT ScriptWrappable {
     WTF_MAKE_NONCOPYABLE(ScriptWrappable);
 public:
     ScriptWrappable() { }
 
     template<typename T>
     T* toImpl()
     {
+        // All ScriptWrappables are managed by the Blink GC heap; check that
+        // |T| is a garbage collected type.
+        static_assert(sizeof(T) && WTF::IsGarbageCollectedType<T>::value, "Classes implementing ScriptWrappable must be garbage collected.");
+
         // Check if T* is castable to ScriptWrappable*, which means T doesn't
         // have two or more ScriptWrappable as superclasses. If T has two
         // ScriptWrappable as superclasses, conversions from T* to
         // ScriptWrappable* are ambiguous.
 #if !COMPILER(MSVC)
         // MSVC 2013 doesn't support static_assert + constexpr well.
         static_assert(!static_cast<ScriptWrappable*>(static_cast<T*>(nullptr)),
             "Class T must not have two or more ScriptWrappable as its superclasses.");
 #endif
         return static_cast<T*>(this);
@@ skipping 89 matching lines @@
         RELEASE_ASSERT(containsWrapper());
         m_wrapper.Reset();
     }
 
     static void firstWeakCallback(const v8::WeakCallbackInfo<ScriptWrappable>& data)
     {
         auto scriptWrappable = data.GetParameter();
         scriptWrappable->disposeWrapper(data);
 
         auto wrapperTypeInfo = reinterpret_cast<WrapperTypeInfo*>(data.GetInternalField(v8DOMWrapperTypeIndex));
-        if (wrapperTypeInfo->isGarbageCollected()) {
-            // derefObject() for garbage collected objects is very cheap, so
-            // we don't delay derefObject to the second pass.
-            //
-            // More importantly, we've already disposed the wrapper at this
-            // moment, so the ScriptWrappable may have already been collected
-            // by GC by the second pass.  We shouldn't use a pointer to the
-            // ScriptWrappable in secondWeakCallback in case of garbage
-            // collected objects.  Thus calls derefObject right now.
-            wrapperTypeInfo->derefObject(scriptWrappable);
-        } else {
-            // For reference counted objects, let's delay the destruction of
-            // the object to the second pass.
-            data.SetSecondPassCallback(secondWeakCallback);
-        }
-    }
-
-    static void secondWeakCallback(const v8::WeakCallbackInfo<ScriptWrappable>& data)
-    {
-        // FIXME: I noticed that 50%~ of minor GC cycle times can be consumed
-        // inside data.GetParameter()->deref(), which causes Node destructions. We should
-        // make Node destructions incremental.
-        auto scriptWrappable = reinterpret_cast<ScriptWrappable*>(data.GetInternalField(v8DOMWrapperObjectIndex));
-        auto wrapperTypeInfo = reinterpret_cast<WrapperTypeInfo*>(data.GetInternalField(v8DOMWrapperTypeIndex));
-        wrapperTypeInfo->derefObject(scriptWrappable);
+        wrapperTypeInfo->wrapperDestroyed();
     }
 
     v8::Persistent<v8::Object> m_wrapper;
 };
 
 // Defines 'wrapperTypeInfo' virtual method which returns the WrapperTypeInfo of
 // the instance. Also declares a static member of type WrapperTypeInfo, of which
 // the definition is given by the IDL code generator.
 //
 // All the derived classes of ScriptWrappable, regardless of directly or
@@ skipping 20 matching lines @@
 // in X's cpp code, and instantiate X, i.e. "template class X;".
 #define DECLARE_WRAPPERTYPEINFO() \
 public: \
     const WrapperTypeInfo* wrapperTypeInfo() const override; \
 private: \
     typedef void end_of_define_wrappertypeinfo_not_reached_t
 
 } // namespace blink
 
 #endif // ScriptWrappable_h