Cleanup usage of scoped_ptr<> in remoting for C++11

remoting/host/setup/daemon_installer_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/host/setup/daemon_installer_win.h"
 
 #include <windows.h>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 364 matching lines @@
   } else if (result == CO_E_CLASSSTRING) {
     // The machine instance of Omaha is not available so we will have to run
     // GoogleUpdate.exe manually passing "needsadmin=True". This will cause
     // Omaha to install the machine instance first and then install Chromoting
     // Host.
     return scoped_ptr<DaemonInstallerWin>(
         new DaemonCommandLineInstallerWin(done));
   } else {
     // The user declined the UAC prompt or some other error occured.
     done.Run(result);
-    return scoped_ptr<DaemonInstallerWin>();
+    return nullptr;
   }
 }
 
 HWND GetTopLevelWindow(HWND window) {
   if (window == NULL) {
     return NULL;
   }
 
   for (;;) {
     LONG style = GetWindowLong(window, GWL_STYLE);
     if ((style & WS_OVERLAPPEDWINDOW) == WS_OVERLAPPEDWINDOW ||
         (style & WS_POPUP) == WS_POPUP) {
       return window;
     }
 
     HWND parent = GetAncestor(window, GA_PARENT);
     if (parent == NULL) {
       return window;
     }
 
     window = parent;
   }
 }
 
 }  // namespace remoting