Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/neteq/delay_manager.cc

Index: webrtc/modules/audio_coding/neteq/delay_manager.cc
diff --git a/webrtc/modules/audio_coding/neteq/delay_manager.cc b/webrtc/modules/audio_coding/neteq/delay_manager.cc
index bc27bd1552ea27df44000667c5e8f50cc804533c..142a3b1a0fb31046af7cecb1c6fb57f926c050f7 100644
--- a/webrtc/modules/audio_coding/neteq/delay_manager.cc
+++ b/webrtc/modules/audio_coding/neteq/delay_manager.cc
@@ -44,7 +44,7 @@ DelayManager::DelayManager(size_t max_packets_in_buffer,
       max_iat_cumulative_sum_(0),
       peak_detector_(*peak_detector),
       last_pack_cng_or_dtmf_(1) {
-  assert(peak_detector);  // Should never be NULL.
+  assert(peak_detector);  // Should never be nullptr.
   Reset();
 }
 
@@ -345,7 +345,7 @@ void DelayManager::ResetPacketIatCount() {
 // class. They are computed from |target_level_| and used for decision making.
 void DelayManager::BufferLimits(int* lower_limit, int* higher_limit) const {
   if (!lower_limit || !higher_limit) {
-    LOG_F(LS_ERROR) << "NULL pointers supplied as input";
+    LOG_F(LS_ERROR) << "null pointers supplied as input";
     assert(false);
     return;
   }