Replace NULL with nullptr in all C++ files.

webrtc/base/task_queue_win.cc

 /*
  *  Copyright 2016 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 22 matching lines @@
   return g_queue_ptr_tls;
 }
 
 struct ThreadStartupData {
   Event* started;
   void* thread_context;
 };
 
 void CALLBACK InitializeQueueThread(ULONG_PTR param) {
   MSG msg;
-  PeekMessage(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);
+  PeekMessage(&msg, nullptr, WM_USER, WM_USER, PM_NOREMOVE);
   ThreadStartupData* data = reinterpret_cast<ThreadStartupData*>(param);
   TlsSetValue(GetQueuePtrTls(), data->thread_context);
   data->started->Set();
 }
 }  // namespace
 
 TaskQueue::TaskQueue(const char* queue_name)
     : thread_(&TaskQueue::ThreadMain, this, queue_name) {
   RTC_DCHECK(queue_name);
   thread_.Start();
@@ skipping 134 matching lines @@
       }
     } else {
       TranslateMessage(&msg);
       DispatchMessage(&msg);
     }
   }
   return msg.message != WM_QUIT;
 }
 
 }  // namespace rtc