Replace NULL with nullptr in all C++ files.

webrtc/base/common.cc

 /*
  *  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 27 matching lines @@
 #else  // !WEBRTC_WIN 
   // On POSIX systems, SIGTRAP signals debuggers to break without killing the
   // process. If a debugger isn't attached, the uncaught SIGTRAP will crash the
   // app.
   raise(SIGTRAP);
 #endif
   // If a debugger wasn't attached, we will have crashed by this point. If a
   // debugger is attached, we'll continue from here.
 }
 
-static AssertLogger custom_assert_logger_ = NULL;
+static AssertLogger custom_assert_logger_ = nullptr;
 
 void SetCustomAssertLogger(AssertLogger logger) {
   custom_assert_logger_ = logger;
 }
 
 void LogAssert(const char* function, const char* file, int line,
                const char* expression) {
   if (custom_assert_logger_) {
     custom_assert_logger_(function, file, line, expression);
   } else {
     LOG(LS_ERROR) << file << "(" << line << ")" << ": ASSERT FAILED: "
                   << expression << " @ " << function;
   }
 }
 
 bool IsOdd(int n) {
   return (n & 0x1);
 }
 
 bool IsEven(int n) {
   return !IsOdd(n);
 }
 
 } // namespace rtc