Replace NULL with nullptr in all C++ files.

webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc b/webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
index c53a2ca5a2f112097060eca3b79af1077ecc4ea6..78634fc1d7025f7d3789a05e68ff36bb9753fa9c 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_format_vp9_unittest.cc
@@ -145,7 +145,7 @@ class RtpPacketizerVp9Test : public ::testing::Test {
     payload_size_ = payload_size;
     payload_pos_ = 0;
     packetizer_.reset(new RtpPacketizerVp9(expected_, packet_size));
-    packetizer_->SetPayloadData(payload_.get(), payload_size_, NULL);
+    packetizer_->SetPayloadData(payload_.get(), payload_size_, nullptr);
   }
 
   void CheckPayload(const uint8_t* packet,
@@ -161,7 +161,7 @@ class RtpPacketizerVp9Test : public ::testing::Test {
   void CreateParseAndCheckPackets(const size_t* expected_hdr_sizes,
                                   const size_t* expected_sizes,
                                   size_t expected_num_packets) {
-    ASSERT_TRUE(packetizer_.get() != NULL);
+    ASSERT_TRUE(packetizer_.get() != nullptr);
     bool last = false;
     if (expected_num_packets == 0) {
       EXPECT_FALSE(packetizer_->NextPacket(&packet_, &last));
@@ -216,7 +216,7 @@ TEST_F(RtpPacketizerVp9Test, TestTooShortBufferToFitPayload) {
   Init(kFrameSize, kPacketSize);  // 1hdr + 1 payload
 
   const size_t kExpectedNum = 0;
-  CreateParseAndCheckPackets(NULL, NULL, kExpectedNum);
+  CreateParseAndCheckPackets(nullptr, nullptr, kExpectedNum);
 }
 
 TEST_F(RtpPacketizerVp9Test, TestOneBytePictureId) {
@@ -340,7 +340,7 @@ TEST_F(RtpPacketizerVp9Test, TestRefIdxFailsWithoutPictureId) {
   Init(kFrameSize, kPacketSize);
 
   const size_t kExpectedNum = 0;
-  CreateParseAndCheckPackets(NULL, NULL, kExpectedNum);
+  CreateParseAndCheckPackets(nullptr, nullptr, kExpectedNum);
 }
 
 TEST_F(RtpPacketizerVp9Test, TestSsDataWithoutSpatialResolutionPresent) {