Reland: Reland: Implement new Blink IDL attribute [SetReference]

Source/bindings/v8/V8DOMWrapper.h

 /*
  * Copyright (C) 2009 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 67 matching lines @@
     template<typename V8T, typename T>
     inline v8::Handle<v8::Object> V8DOMWrapper::associateObjectWithWrapper(PassRefPtr<T> object, const WrapperTypeInfo* type, v8::Handle<v8::Object> wrapper, v8::Isolate* isolate, WrapperConfiguration::Lifetime lifetime)
     {
         setNativeInfo(wrapper, type, V8T::toInternalPointer(object.get()));
         ASSERT(maybeDOMWrapper(wrapper));
         WrapperConfiguration configuration = buildWrapperConfiguration(object.get(), lifetime);
         DOMDataStore::setWrapper<V8T>(object.leakRef(), wrapper, isolate, configuration);
         return wrapper;
     }
 
+    class V8WrapperInstantiationScope {
+    public:
+        V8WrapperInstantiationScope(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
+            : m_didEnterContext(false)
+            , m_context(v8::Context::GetCurrent())
+        {
+            // FIXME: Remove all empty creationContexts from caller sites.
+            // If a creationContext is empty, we will end up creating a new object
+            // in the context currently entered. This is wrong.
+            if (creationContext.IsEmpty())
+                return;
+            v8::Handle<v8::Context> contextForWrapper = creationContext->CreationContext();
+            // For performance, we enter the context only if the currently running context
+            // is different from the context that we are about to enter.
+            if (contextForWrapper == m_context)
+                return;
+            m_context = v8::Local<v8::Context>::New(isolate, contextForWrapper);
+            m_didEnterContext = true;
+            m_context->Enter();
+        }
+
+        ~V8WrapperInstantiationScope()
+        {
+            if (!m_didEnterContext)
+                return;
+            m_context->Exit();
+        }
+
+        v8::Handle<v8::Context> context() const { return m_context; }
+
+    private:
+        bool m_didEnterContext;
+        v8::Handle<v8::Context> m_context;
+    };
+
 }
 
 #endif // V8DOMWrapper_h