replace NULL->nullptr in src/remoting.

remoting/host/win/rdp_client_unittest.cc

Index: remoting/host/win/rdp_client_unittest.cc
diff --git a/remoting/host/win/rdp_client_unittest.cc b/remoting/host/win/rdp_client_unittest.cc
index 4ef67b6fcafa2d76eeb49672d795ff3fb2a86b13..1b37d5c38b903f0401eebc091e6c7175de6a39ed 100644
--- a/remoting/host/win/rdp_client_unittest.cc
+++ b/remoting/host/win/rdp_client_unittest.cc
@@ -71,7 +71,7 @@ RdpClientModule::RdpClientModule() {
 
 RdpClientModule::~RdpClientModule() {
   AtlAxWinTerm();
-  ATL::_pAtlModule = NULL;
+  ATL::_pAtlModule = nullptr;
 }
 
 }  // namespace
@@ -165,7 +165,7 @@ TEST_F(RdpClientTest, Basic) {
       task_runner_, task_runner_,
       webrtc::DesktopSize(kDefaultWidth, kDefaultHeight),
       terminal_id_, &event_handler_));
-  task_runner_ = NULL;
+  task_runner_ = nullptr;
 
   run_loop_.Run();
 }