replace NULL->nullptr in src/remoting.

Review URL: https://codereview.chromium.org/810133003

Cr-Commit-Position: refs/heads/master@{#310816}
diff --git a/remoting/host/desktop_session_win.cc b/remoting/host/desktop_session_win.cc
index 35fb4f46..c98f229 100644
--- a/remoting/host/desktop_session_win.cc
+++ b/remoting/host/desktop_session_win.cc
@@ -334,7 +334,7 @@
     return S_OK;
   }
 
-  *ppv = NULL;
+  *ppv = nullptr;
   return E_NOINTERFACE;
 }