Simplify SelfKeepAlive<T>'s representation.

Source/platform/heap/Handle.h

 /*
  * Copyright (C) 2014 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 1137 matching lines @@
     {
         assign(self);
         return *this;
     }
 
     void clear()
     {
         m_keepAlive.clear();
     }
 
-    typedef OwnPtr<Persistent<Self>> (SelfKeepAlive::*UnspecifiedBoolType);
+    typedef Persistent<Self> (SelfKeepAlive::*UnspecifiedBoolType);
     operator UnspecifiedBoolType() const { return m_keepAlive ? &SelfKeepAlive::m_keepAlive : 0; }
 
 private:
     void assign(Self* self)
     {
-        ASSERT(!m_keepAlive || m_keepAlive->get() == self);
-        if (!m_keepAlive)
-            m_keepAlive = adoptPtr(new Persistent<Self>);
-        *m_keepAlive = self;
+        ASSERT(!m_keepAlive || m_keepAlive.get() == self);
+        m_keepAlive = self;
     }
 
     GC_PLUGIN_IGNORE("420515")
-    OwnPtr<Persistent<Self>> m_keepAlive;
+    Persistent<Self> m_keepAlive;
 };
 
 template<typename T>
 class AllowCrossThreadWeakPersistent {
     STACK_ALLOCATED();
 public:
     explicit AllowCrossThreadWeakPersistent(T* value) : m_value(value) { }
     CrossThreadWeakPersistent<T> value() const { return m_value; }
 private:
     CrossThreadWeakPersistent<T> m_value;
@@ skipping 200 matching lines @@
     // TODO(sof): extend WTF::FunctionWrapper call overloading to also handle (CrossThread)WeakPersistent.
     static T* unwrap(const StorageType& value) { return value.get(); }
 };
 
 template<typename T>
 PassRefPtr<T> adoptRef(blink::RefCountedGarbageCollected<T>*) = delete;
 
 } // namespace WTF
 
 #endif