Oilpan: restrict implicit RawPtr<U> conversions; U must be T-convertible.

Source/wtf/RawPtr.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 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WTF_RawPtr_h
 #define WTF_RawPtr_h
 
 #include <algorithm>
 #include <stdint.h>
 
 #include "wtf/HashTableDeletedValueType.h"
+#include "wtf/TypeTraits.h"
 
 // RawPtr is a simple wrapper for a raw pointer that provides the
 // interface (get, clear) of other pointer types such as RefPtr,
 // Persistent and Member. This is used for the Blink garbage
 // collection work in order to be able to write shared code that will
 // use reference counting or garbage collection based on a
 // compile-time flag.
 
 namespace WTF {
 
 template<typename T>
 class RawPtr {
 public:
     RawPtr()
     {
 #if ENABLE(ASSERT)
         m_ptr = reinterpret_cast<T*>(rawPtrZapValue);
 #endif
     }
     RawPtr(std::nullptr_t) : m_ptr(0) { }
     RawPtr(T* ptr) : m_ptr(ptr) { }
     explicit RawPtr(T& reference) : m_ptr(&reference) { }
     RawPtr(const RawPtr& other)
         : m_ptr(other.get())
     {
     }
 
     template<typename U>
-    RawPtr(const RawPtr<U>& other)
+    RawPtr(const RawPtr<U>& other, EnsurePtrConvertibleArgDecl(U, T))
         : m_ptr(other.get())
     {
     }
 
     // Hash table deleted values, which are only constructed and never copied or destroyed.
     RawPtr(HashTableDeletedValueType) : m_ptr(hashTableDeletedValue()) { }
     bool isHashTableDeletedValue() const { return m_ptr == hashTableDeletedValue(); }
 
     T* get() const { return m_ptr; }
     void clear() { m_ptr = 0; }
@@ skipping 62 matching lines @@
 template<typename T> inline T* getPtr(const RawPtr<T>& p)
 {
     return p.get();
 }
 
 } // namespace WTF
 
 using WTF::RawPtr;
 
 #endif