Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/unixfilesystem.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 17 matching lines @@
   // only supports an Objective-C API for fetching the folder locations, so that
   // needs to be passed in here from Objective-C.  Or at least that used to be
   // the case; now the ctor will do the work if necessary and possible.
   // TODO(fischman): add an Android version that uses JNI and drop the
   // SetApp*Folder() APIs once external users stop using them.
   static void SetAppDataFolder(const std::string& folder);
   static void SetAppTempFolder(const std::string& folder);
 #endif
 
   // Opens a file. Returns an open StreamInterface if function succeeds.
-  // Otherwise, returns NULL.
+  // Otherwise, returns null.
   FileStream* OpenFile(const Pathname& filename,
                        const std::string& mode) override;
 
   // This will attempt to delete the file located at filename.
   // It will fail with VERIY if you pass it a non-existant file, or a directory.
   bool DeleteFile(const Pathname& filename) override;
 
   // This will attempt to delete the folder located at 'folder'
   // It DCHECKs and returns false if you pass it a non-existant folder or a
   // plain file.
@@ skipping 55 matching lines @@
 #else
   static char* app_temp_path_;
 #endif
 
   static char* CopyString(const std::string& str);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_UNIXFILESYSTEM_H_