Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc

Index: webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
diff --git a/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc b/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
index 8506e326cb48cd15410cd5c950cf5348f1523afd..3543a242654c75191a014595e9821fcf94ba7c7d 100644
--- a/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
+++ b/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
@@ -54,14 +54,14 @@ NetEqIsacQualityTest::NetEqIsacQualityTest()
                        kIsacInputSamplingKhz,
                        kIsacOutputSamplingKhz,
                        NetEqDecoder::kDecoderISAC),
-      isac_encoder_(NULL),
+      isac_encoder_(nullptr),
       bit_rate_kbps_(FLAGS_bit_rate_kbps) {}
 
 void NetEqIsacQualityTest::SetUp() {
   ASSERT_EQ(1u, channels_) << "iSAC supports only mono audio.";
   // Create encoder memory.
   WebRtcIsacfix_Create(&isac_encoder_);
-  ASSERT_TRUE(isac_encoder_ != NULL);
+  ASSERT_TRUE(isac_encoder_ != nullptr);
   EXPECT_EQ(0, WebRtcIsacfix_EncoderInit(isac_encoder_, 1));
   // Set bitrate and block length.
   EXPECT_EQ(0, WebRtcIsacfix_Control(isac_encoder_, bit_rate_kbps_ * 1000,