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

webrtc/base/thread_checker_unittest.cc

 /*
  *  Copyright (c) 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.
  */
 
@@ skipping 36 matching lines @@
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(ThreadCheckerClass);
 };
 
 // Calls ThreadCheckerClass::DoStuff on another thread.
 class CallDoStuffOnThread : public Thread {
  public:
   explicit CallDoStuffOnThread(ThreadCheckerClass* thread_checker_class)
       : Thread(),
         thread_checker_class_(thread_checker_class) {
-    SetName("call_do_stuff_on_thread", NULL);
+    SetName("call_do_stuff_on_thread", nullptr);
   }
 
   void Run() override { thread_checker_class_->DoStuff(); }
 
   // New method. Needed since Thread::Join is protected, and it is called by
   // the TEST.
   void Join() {
     Thread::Join();
   }
 
  private:
   ThreadCheckerClass* thread_checker_class_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(CallDoStuffOnThread);
 };
 
 // Deletes ThreadCheckerClass on a different thread.
 class DeleteThreadCheckerClassOnThread : public Thread {
  public:
   explicit DeleteThreadCheckerClassOnThread(
       ThreadCheckerClass* thread_checker_class)
       : Thread(),
         thread_checker_class_(thread_checker_class) {
-    SetName("delete_thread_checker_class_on_thread", NULL);
+    SetName("delete_thread_checker_class_on_thread", nullptr);
   }
 
   void Run() override { thread_checker_class_.reset(); }
 
   // New method. Needed since Thread::Join is protected, and it is called by
   // the TEST.
   void Join() {
     Thread::Join();
   }
 
@@ skipping 151 matching lines @@
 
   int var_thread_ ACCESS_ON(thread_);
   int var_checker_ GUARDED_BY(checker_);
   int var_queue_ ACCESS_ON(queue_);
 };
 
 // Just in case we ever get lumped together with other compilation units.
 #undef ENABLE_THREAD_CHECKER
 
 }  // namespace rtc