replace NULL->nullptr in src/remoting.

remoting/host/pairing_registry_delegate_win.h

Index: remoting/host/pairing_registry_delegate_win.h
diff --git a/remoting/host/pairing_registry_delegate_win.h b/remoting/host/pairing_registry_delegate_win.h
index 844f6af3e38e3d6cfc68f2181af2b61c6f13e817..9f9d4dce2d5411b5894927f177cb08b5b76b3678 100644
--- a/remoting/host/pairing_registry_delegate_win.h
+++ b/remoting/host/pairing_registry_delegate_win.h
@@ -38,7 +38,7 @@ const wchar_t kPairingRegistrySecretsKeyName[] = L"secrets";
 //  - |unprivileged| - contains the rest of pairing state.
 //
 // Creator of this object is responsible for passing the registry key handles
-// with appropriate access. |privileged| may be NULL if read-only access is
+// with appropriate access. |privileged| may be nullptr if read-only access is
 // sufficient. Shared secrets will not be returned in such a case.
 class PairingRegistryDelegateWin
     : public protocol::PairingRegistry::Delegate {
@@ -47,8 +47,8 @@ class PairingRegistryDelegateWin
   virtual ~PairingRegistryDelegateWin();
 
   // Passes the root keys to be used to access the pairing registry store.
-  // |privileged| is optional and may be NULL. The caller retains ownership of
-  // the passed handles.
+  // |privileged| is optional and may be nullptr. The caller retains ownership
+  // of the passed handles.
   bool SetRootKeys(HKEY privileged, HKEY unprivileged);
 
   // PairingRegistry::Delegate interface