Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc

Index: webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc
diff --git a/webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc b/webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc
index e8795a9a1560637ad40d75491104ad9ef3537535..db24727d2b26882ee5bf1d55d5e8df85dbfa7f8a 100644
--- a/webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc
+++ b/webrtc/modules/audio_coding/neteq/packet_buffer_unittest.cc
@@ -450,7 +450,7 @@ TEST(PacketBuffer, Failures) {
   EXPECT_EQ(PacketBuffer::kBufferEmpty, buffer->NextTimestamp(&temp_ts));
   EXPECT_EQ(PacketBuffer::kBufferEmpty,
             buffer->NextHigherTimestamp(0, &temp_ts));
-  EXPECT_EQ(NULL, buffer->PeekNextPacket());
+  EXPECT_EQ(nullptr, buffer->PeekNextPacket());
   EXPECT_FALSE(buffer->GetNextPacket());
   EXPECT_EQ(PacketBuffer::kBufferEmpty, buffer->DiscardNextPacket());
   EXPECT_EQ(0, buffer->DiscardAllOldPackets(0));  // 0 packets discarded.
@@ -458,9 +458,9 @@ TEST(PacketBuffer, Failures) {
   // Insert one packet to make the buffer non-empty.
   EXPECT_EQ(PacketBuffer::kOK,
             buffer->InsertPacket(gen.NextPacket(payload_len)));
-  EXPECT_EQ(PacketBuffer::kInvalidPointer, buffer->NextTimestamp(NULL));
+  EXPECT_EQ(PacketBuffer::kInvalidPointer, buffer->NextTimestamp(nullptr));
   EXPECT_EQ(PacketBuffer::kInvalidPointer,
-            buffer->NextHigherTimestamp(0, NULL));
+            buffer->NextHigherTimestamp(0, nullptr));
   delete buffer;
 
   // Insert packet list of three packets, where the second packet has an invalid