Made RefPtr constructor only accept PassRefPtr rvalues.

third_party/WebKit/Source/platform/wtf/RefPtr.h

 /*
  *  Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc.
  *  All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
@@ skipping 38 matching lines @@
   template <typename U>
   RefPtr(const RefPtr<U>& o, EnsurePtrConvertibleArgDecl(U, T))
       : ptr_(o.Get()) {
     RefIfNotNull(ptr_);
   }
   RefPtr(RefPtr&& o) : ptr_(o.ptr_) { o.ptr_ = nullptr; }
 
   // See comments in PassRefPtr.h for an explanation of why this takes a const
   // reference.
   template <typename U>
-  RefPtr(const PassRefPtr<U>&, EnsurePtrConvertibleArgDecl(U, T));
+  RefPtr(PassRefPtr<U>&&, EnsurePtrConvertibleArgDecl(U, T));
 
   // Hash table deleted values, which are only constructed and never copied or
   // destroyed.
   RefPtr(HashTableDeletedValueType) : ptr_(HashTableDeletedValue()) {}
   bool IsHashTableDeletedValue() const {
     return ptr_ == HashTableDeletedValue();
   }
 
   ALWAYS_INLINE ~RefPtr() { DerefIfNotNull(ptr_); }
 
@@ skipping 27 matching lines @@
   void Swap(RefPtr&);
 
   static T* HashTableDeletedValue() { return reinterpret_cast<T*>(-1); }
 
  private:
   T* ptr_;
 };
 
 template <typename T>
 template <typename U>
-inline RefPtr<T>::RefPtr(const PassRefPtr<U>& o,
-                         EnsurePtrConvertibleArgDefn(U, T))
+inline RefPtr<T>::RefPtr(PassRefPtr<U>&& o, EnsurePtrConvertibleArgDefn(U, T))
     : ptr_(o.LeakRef()) {}
 
 template <typename T>
 inline T* RefPtr<T>::LeakRef() {
   T* ptr = ptr_;
   ptr_ = nullptr;
   return ptr;
 }
 
 template <typename T>
@@ skipping 92 matching lines @@
 
  private:
   T* ptr_;
 };
 
 }  // namespace WTF
 
 using WTF::RefPtr;
 
 #endif  // WTF_RefPtr_h