Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc

Index: webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc
diff --git a/webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc b/webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc
index 3f7170c30b63014f291e368d28d28f270ff65605..1bc186807956af3185a01fa0dff04b4f5fab4c65 100644
--- a/webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc
+++ b/webrtc/modules/audio_coding/codecs/isac/main/source/isac_unittest.cc
@@ -35,9 +35,7 @@ class IsacTest : public ::testing::Test {
   uint8_t bitstream_small_[7];  // Simulate sync packets.
 };
 
-IsacTest::IsacTest()
-    : isac_codec_(NULL) {
-}
+IsacTest::IsacTest() : isac_codec_(nullptr) {}
 
 void IsacTest::SetUp() {
   // Read some samples from a speech file, to be used in the encode test.
@@ -45,30 +43,30 @@ void IsacTest::SetUp() {
   const std::string file_name =
         webrtc::test::ResourcePath("audio_coding/testfile32kHz", "pcm");
   input_file = fopen(file_name.c_str(), "rb");
-  ASSERT_TRUE(input_file != NULL);
+  ASSERT_TRUE(input_file != nullptr);
   ASSERT_EQ(kIsacNumberOfSamples,
             static_cast<int32_t>(fread(speech_data_, sizeof(int16_t),
                                        kIsacNumberOfSamples, input_file)));
   fclose(input_file);
-  input_file = NULL;
+  input_file = nullptr;
 }
 
 // Test failing Create.
 TEST_F(IsacTest, IsacCreateFail) {
   // Test to see that an invalid pointer is caught.
-  EXPECT_EQ(-1, WebRtcIsac_Create(NULL));
+  EXPECT_EQ(-1, WebRtcIsac_Create(nullptr));
 }
 
 // Test failing Free.
 TEST_F(IsacTest, IsacFreeFail) {
   // Test to see that free function doesn't crash.
-  EXPECT_EQ(0, WebRtcIsac_Free(NULL));
+  EXPECT_EQ(0, WebRtcIsac_Free(nullptr));
 }
 
 // Test normal Create and Free.
 TEST_F(IsacTest, IsacCreateFree) {
   EXPECT_EQ(0, WebRtcIsac_Create(&isac_codec_));
-  EXPECT_TRUE(isac_codec_ != NULL);
+  EXPECT_TRUE(isac_codec_ != nullptr);
   EXPECT_EQ(0, WebRtcIsac_Free(isac_codec_));}
 
 TEST_F(IsacTest, IsacUpdateBWE) {