Replace NULL with nullptr in all C++ files.

webrtc/test/rtp_file_writer_unittest.cc

Index: webrtc/test/rtp_file_writer_unittest.cc
diff --git a/webrtc/test/rtp_file_writer_unittest.cc b/webrtc/test/rtp_file_writer_unittest.cc
index fa7d79d039a7b11b0789d5023106c19419779918..ea29ed480c971796cb34af6347e3a645a8859e51 100644
--- a/webrtc/test/rtp_file_writer_unittest.cc
+++ b/webrtc/test/rtp_file_writer_unittest.cc
@@ -28,7 +28,7 @@ class RtpFileWriterTest : public ::testing::Test {
   }
 
   void WriteRtpPackets(int num_packets) {
-    ASSERT_TRUE(rtp_writer_.get() != NULL);
+    ASSERT_TRUE(rtp_writer_.get() != nullptr);
     test::RtpPacket packet;
     for (int i = 1; i <= num_packets; ++i) {
       packet.length = i;
@@ -42,11 +42,11 @@ class RtpFileWriterTest : public ::testing::Test {
   void CloseOutputFile() { rtp_writer_.reset(); }
 
   void VerifyFileContents(int expected_packets) {
-    ASSERT_TRUE(rtp_writer_.get() == NULL)
+    ASSERT_TRUE(rtp_writer_.get() == nullptr)
         << "Must call CloseOutputFile before VerifyFileContents";
     std::unique_ptr<test::RtpFileReader> rtp_reader(
         test::RtpFileReader::Create(test::RtpFileReader::kRtpDump, filename_));
-    ASSERT_TRUE(rtp_reader.get() != NULL);
+    ASSERT_TRUE(rtp_reader.get() != nullptr);
     test::RtpPacket packet;
     int i = 0;
     while (rtp_reader->NextPacket(&packet)) {