Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc

Index: webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
diff --git a/webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc b/webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
index fff8ee303c4664cfbe418dc9af70defc585455ca..ffe9152d432a210f509b79db12ca3370f3259772 100644
--- a/webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
+++ b/webrtc/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
@@ -53,7 +53,7 @@ class AudioEncoderCopyRedTest : public ::testing::Test {
   }
 
   void Encode() {
-    ASSERT_TRUE(red_.get() != NULL);
+    ASSERT_TRUE(red_.get() != nullptr);
     encoded_.Clear();
     encoded_info_ = red_->Encode(
         timestamp_,
@@ -293,9 +293,9 @@ TEST_F(AudioEncoderCopyRedDeathTest, WrongFrameSize) {
 }
 
 TEST_F(AudioEncoderCopyRedDeathTest, NullSpeechEncoder) {
-  AudioEncoderCopyRed* red = NULL;
+  AudioEncoderCopyRed* red = nullptr;
   AudioEncoderCopyRed::Config config;
-  config.speech_encoder = NULL;
+  config.speech_encoder = nullptr;
   EXPECT_DEATH(red = new AudioEncoderCopyRed(std::move(config)),
                "Speech encoder not provided.");
   // The delete operation is needed to avoid leak reports from memcheck.