Replace NULL with nullptr in all C++ files.

webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc

Index: webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc
diff --git a/webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc b/webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc
index 2938b411e4699de39bce7c94310402e8edc8bf5f..802d8e4d6bd9619cc68f526c0804858fe4fd0724 100644
--- a/webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc
+++ b/webrtc/voice_engine/test/channel_transport/udp_transport_unittest.cc
@@ -118,8 +118,8 @@ TEST_F(UDPTransportTest, CreateTransport) {
 // This test verifies that the mock_socket is not called from the constructor.
 TEST_F(UDPTransportTest, ConstructorDoesNotCreateSocket) {
   int32_t id = 0;
-  UdpTransportImpl::SocketFactoryInterface* null_maker = NULL;
-  UdpSocketManager* null_manager = NULL;
+  UdpTransportImpl::SocketFactoryInterface* null_maker = nullptr;
+  UdpSocketManager* null_manager = nullptr;
   UdpTransport* transport = new UdpTransportImpl(id,
                                                  null_maker,
                                                  null_manager);