C++11 declares a type safe null pointer

content/common/gpu/client/gpu_video_encode_accelerator_host.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 CONTENT_COMMON_GPU_CLIENT_GPU_VIDEO_ENCODE_ACCELERATOR_HOST_H_
 #define CONTENT_COMMON_GPU_CLIENT_GPU_VIDEO_ENCODE_ACCELERATOR_HOST_H_
 
 #include <vector>
 
 #include "base/containers/hash_tables.h"
@@ skipping 70 matching lines @@
                                  const gfx::Size& input_coded_size,
                                  uint32 output_buffer_size);
   void OnNotifyInputDone(int32 frame_id);
   void OnBitstreamBufferReady(int32 bitstream_buffer_id,
                               uint32 payload_size,
                               bool key_frame);
   void OnNotifyError(Error error);
 
   // Unowned reference to the GpuChannelHost to send IPC messages to the GPU
   // process.  |channel_| outlives |impl_|, so the reference is always valid as
-  // long as it is not NULL.
+  // long as it is not nullptr.
   GpuChannelHost* channel_;
 
   // Route ID for the associated encoder in the GPU process.
   int32 encoder_route_id_;
 
   // The client that will receive callbacks from the encoder.
   Client* client_;
 
   // Unowned reference to the CommandBufferProxyImpl that created us.  |this|
   // registers as a DeletionObserver of |impl_|, so the reference is always
-  // valid as long as it is not NULL.
+  // valid as long as it is not nullptr.
   CommandBufferProxyImpl* impl_;
 
   // media::VideoFrames sent to the encoder.
   // base::IDMap not used here, since that takes pointers, not scoped_refptr.
   typedef base::hash_map<int32, scoped_refptr<media::VideoFrame> > FrameMap;
   FrameMap frame_map_;
 
   // ID serial number for the next frame to send to the GPU process.
   int32 next_frame_id_;
 
   // WeakPtr factory for posting tasks back to itself.
   base::WeakPtrFactory<GpuVideoEncodeAcceleratorHost> weak_this_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuVideoEncodeAcceleratorHost);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_CLIENT_GPU_VIDEO_ENCODE_ACCELERATOR_HOST_H_