bindings: Introduces type-check for the internal pointers.

Source/bindings/core/v8/NPV8Object.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Google Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. 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.
@@ skipping 23 matching lines @@
 #include "bindings/core/v8/V8DOMWrapper.h"
 
 // Chromium uses npruntime.h from the Chromium source repository under
 // third_party/npapi/bindings.
 #include <bindings/npruntime.h>
 #include <v8.h>
 
 namespace blink {
 
 class LocalDOMWindow;
+class ScriptWrappableBase;
 
 static const int npObjectInternalFieldCount = v8DefaultWrapperInternalFieldCount + 0;
 
 const WrapperTypeInfo* npObjectTypeInfo();
 
 // A V8NPObject is a NPObject which carries additional V8-specific information.
 // It is created with npCreateV8ScriptObject() and deallocated via the deallocate
 // method in the same way as other NPObjects.
 struct V8NPObject {
     WTF_MAKE_NONCOPYABLE(V8NPObject);
@@ skipping 12 matching lines @@
 };
 
 NPObject* npCreateV8ScriptObject(NPP, v8::Handle<v8::Object>, LocalDOMWindow*, v8::Isolate*);
 
 NPObject* v8ObjectToNPObject(v8::Handle<v8::Object>);
 
 bool isWrappedNPObject(v8::Handle<v8::Object>);
 
 V8NPObject* npObjectToV8NPObject(NPObject*);
 
+ScriptWrappableBase* npObjectToInternalPointer(NPObject*);
+
 void disposeUnderlyingV8Object(NPObject*, v8::Isolate*);
 
 } // namespace blink
 
 #endif // NPV8Object_h