bindings: Introduces type-check for the internal pointers.

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 39 matching lines @@
  *
  * This class provides the internal pointer to be stored in the wrapper objects,
  * and its conversions from / to the DOM instances.
  *
  * Note that this class must not have vtbl (any virtual function) or any member
  * variable which increase the size of instances.  Some of the classes sensitive
  * to the size inherit from this class.  So this class must be zero size.
  */
 class ScriptWrappableBase {
 public:
-    template <class T> static T* fromInternalPointer(void* internalPointer)
+    template <class T> static T* fromInternalPointer(ScriptWrappableBase* internalPointer)
     {
         // Check if T* is castable to ScriptWrappableBase*, which means T
         // doesn't have two or more ScriptWrappableBase as superclasses.
         // If T has two ScriptWrappableBase as superclasses, conversions
         // from T* to ScriptWrappableBase* are ambiguous.
-        ASSERT(static_cast<ScriptWrappableBase*>(static_cast<T*>(static_cast<ScriptWrappableBase*>(internalPointer))));
-        return static_cast<T*>(static_cast<ScriptWrappableBase*>(internalPointer));
+        ASSERT(static_cast<ScriptWrappableBase*>(static_cast<T*>(internalPointer)));
+        return static_cast<T*>(internalPointer);
     }
-    void* toInternalPointer() { return this; }
+    ScriptWrappableBase* toInternalPointer() { return this; }
 };
 
 /**
  * ScriptWrappable wraps a V8 object and its WrapperTypeInfo.
  *
  * ScriptWrappable acts much like a v8::Persistent<> in that it keeps a
  * V8 object alive. Under the hood, however, it keeps either a TypeInfo
  * object or an actual v8 persistent (or is empty).
  *
  * The physical state space of ScriptWrappable is:
@@ skipping 218 matching lines @@
         // 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.
         releaseObject(data.GetValue());
     }
 };
 
 } // namespace blink
 
 #endif // ScriptWrappable_h