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

webrtc/base/platform_file.cc

 /*
  *  Copyright 2014 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.
  */
 
 #include "webrtc/base/platform_file.h"
 
 #if defined(WEBRTC_WIN)
 #include <io.h>
 #else
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 #endif
 
 namespace rtc {
 
 #if defined(WEBRTC_WIN)
 const PlatformFile kInvalidPlatformFileValue = INVALID_HANDLE_VALUE;
 
 FILE* FdopenPlatformFileForWriting(PlatformFile file) {
   if (file == kInvalidPlatformFileValue)
-    return NULL;
+    return nullptr;
   int fd = _open_osfhandle(reinterpret_cast<intptr_t>(file), 0);
   if (fd < 0)
-    return NULL;
+    return nullptr;
 
   return _fdopen(fd, "w");
 }
 
 bool ClosePlatformFile(PlatformFile file) {
   return CloseHandle(file) != 0;
 }
 
 bool RemoveFile(const std::string& path) {
   return ::DeleteFile(ToUtf16(path).c_str()) != 0;
@@ skipping 29 matching lines @@
   return ::open(path.c_str(), O_RDWR);
 }
 
 PlatformFile CreatePlatformFile(const std::string& path) {
   return ::open(path.c_str(), O_CREAT | O_TRUNC | O_RDWR, S_IRUSR | S_IWUSR);
 }
 
 #endif
 
 }  // namespace rtc