[C++11 Allowed Features] Declares a type-safe null pointer converting from NULL to nullptr

cc/base/swap_promise_monitor.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_BASE_SWAP_PROMISE_MONITOR_H_
 #define CC_BASE_SWAP_PROMISE_MONITOR_H_
 
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
 class LayerTreeHost;
 class LayerTreeHostImpl;
 
 // A SwapPromiseMonitor is used to monitor compositor state change that
 // should be associated with a SwapPromise, e.g. SetNeedsCommit() is
 // called on main thread or SetNeedsRedraw() is called on impl thread.
 // Creating a SwapPromiseMonitor will insert itself into a LayerTreeHost
 // or LayerTreeHostImpl. You must provide a pointer to the appropriate
 // structure to the monitor (and only one of the two). Notification of
 // compositor state change will be sent through OnSetNeedsCommitOnMain()
 // or OnSetNeedsRedrawOnImpl(). When SwapPromiseMonitor is destroyed, it
 // will unregister itself from LayerTreeHost or LayerTreeHostImpl.
 class CC_EXPORT SwapPromiseMonitor {
  public:
   // If the monitor lives on the main thread, pass in layer_tree_host
-  // and set layer_tree_host_impl to NULL.
+  // and set layer_tree_host_impl to nullptr.
   // If the monitor lives on the impl thread, pass in layer_tree_host_impl
-  // and set layer_tree_host to NULL.
+  // and set layer_tree_host to nullptr.
   SwapPromiseMonitor(LayerTreeHost* layer_tree_host,
                      LayerTreeHostImpl* layer_tree_host_impl);
   virtual ~SwapPromiseMonitor();
 
   virtual void OnSetNeedsCommitOnMain() = 0;
   virtual void OnSetNeedsRedrawOnImpl() = 0;
   virtual void OnForwardScrollUpdateToMainThreadOnImpl() = 0;
 
  protected:
   LayerTreeHost* layer_tree_host_;
   LayerTreeHostImpl* layer_tree_host_impl_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_SWAP_PROMISE_MONITOR_H_