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

webrtc/base/thread.h

Index: webrtc/base/thread.h
diff --git a/webrtc/base/thread.h b/webrtc/base/thread.h
index 58fa3f0d463b5ee0c6e1f83ae5fc4aaadcc875e6..5751df385cc5d1acd43f8b153d3af0720ceb7a6f 100644
--- a/webrtc/base/thread.h
+++ b/webrtc/base/thread.h
@@ -56,7 +56,7 @@ class ThreadManager {
   // unexpected contexts (like inside browser plugins) and it would be a
   // shame to break it.  It is also conceivable on Win32 that we won't even
   // be able to get synchronization privileges, in which case the result
-  // will have a NULL handle.
+  // will have a null handle.
   Thread *WrapCurrentThread();
   void UnwrapCurrentThread();
 
@@ -133,12 +133,12 @@ class LOCKABLE Thread : public MessageQueue {
   static bool SleepMs(int millis);
 
   // Sets the thread's name, for debugging. Must be called before Start().
-  // If |obj| is non-NULL, its value is appended to |name|.
+  // If |obj| is non-null, its value is appended to |name|.
   const std::string& name() const { return name_; }
   bool SetName(const std::string& name, const void* obj);
 
   // Starts the execution of the thread.
-  bool Start(Runnable* runnable = NULL);
+  bool Start(Runnable* runnable = nullptr);
 
   // Tells the thread to stop and waits until it is joined.
   // Never call Stop on the current thread.  Instead use the inherited Quit
@@ -154,7 +154,7 @@ class LOCKABLE Thread : public MessageQueue {
   virtual void Send(const Location& posted_from,
                     MessageHandler* phandler,
                     uint32_t id = 0,
-                    MessageData* pdata = NULL);
+                    MessageData* pdata = nullptr);
 
   // Convenience method to invoke a functor on another thread.  Caller must
   // provide the |ReturnT| template argument, which cannot (easily) be deduced.
@@ -174,7 +174,7 @@ class LOCKABLE Thread : public MessageQueue {
   // From MessageQueue
   void Clear(MessageHandler* phandler,
              uint32_t id = MQID_ANY,
-             MessageList* removed = NULL) override;
+             MessageList* removed = nullptr) override;
   void ReceiveSends() override;
 
   // ProcessMessages will process I/O and dispatch messages until:
@@ -255,11 +255,11 @@ class LOCKABLE Thread : public MessageQueue {
   // Return true if the thread was started and hasn't yet stopped.
   bool running() { return running_.Wait(0); }
 
-  // Processes received "Send" requests. If |source| is not NULL, only requests
+  // Processes received "Send" requests. If |source| is not null, only requests
   // from |source| are processed, otherwise, all requests are processed.
   void ReceiveSendsFromThread(const Thread* source);
 
-  // If |source| is not NULL, pops the first "Send" message from |source| in
+  // If |source| is not null, pops the first "Send" message from |source| in
   // |sendlist_|, otherwise, pops the first "Send" message of |sendlist_|.
   // The caller must lock |crit_| before calling.
   // Returns true if there is such a message.