Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/animation/Player.cpp

 /*
  * Copyright (C) 2013 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 278 matching lines @@
     return m_content->timeToReverseEffectChange() / abs(m_playbackRate);
 }
 
 void Player::cancel()
 {
     if (!m_content)
         return;
 
     ASSERT(m_content->player() == this);
     m_content->detach();
-    m_content = 0;
+    m_content = nullptr;
 }
 
 void Player::pauseForTesting(double pauseTime)
 {
     RELEASE_ASSERT(!paused());
     updateTimingState(pauseTime);
     if (!m_isPausedForTesting && hasActiveAnimationsOnCompositor())
         toAnimation(m_content.get())->pauseAnimationForTestingOnCompositor(currentTime());
     m_isPausedForTesting = true;
     pause();
 }
 
 } // namespace