Rewrite scoped_ptr<T>(NULL) to use the default ctor in remoting/.

remoting/protocol/me2me_host_authenticator_factory.cc

Index: remoting/protocol/me2me_host_authenticator_factory.cc
diff --git a/remoting/protocol/me2me_host_authenticator_factory.cc b/remoting/protocol/me2me_host_authenticator_factory.cc
index eddc50ff5c173f1e0db5fbd53fb261007d514263..d0deff1f5574e8d259404edd4718365b6f767f08 100644
--- a/remoting/protocol/me2me_host_authenticator_factory.cc
+++ b/remoting/protocol/me2me_host_authenticator_factory.cc
@@ -43,13 +43,13 @@ class RejectingAuthenticator : public Authenticator {
 
   virtual scoped_ptr<buzz::XmlElement> GetNextMessage() OVERRIDE {
     NOTREACHED();
-    return scoped_ptr<buzz::XmlElement>(NULL);
+    return scoped_ptr<buzz::XmlElement>();
   }
 
   virtual scoped_ptr<ChannelAuthenticator>
   CreateChannelAuthenticator() const OVERRIDE {
     NOTREACHED();
-    return scoped_ptr<ChannelAuthenticator>(NULL);
+    return scoped_ptr<ChannelAuthenticator>();
   }
 
  protected: