[CleanUp] Use base::STLSetDifference in place of std::set_difference

chrome/common/extensions/permissions/permission_set.cc

 // Copyright (c) 2013 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 "chrome/common/extensions/permissions/permission_set.h"
 
 #include <algorithm>
 #include <iterator>
 #include <string>
 
@@ skipping 525 matching lines @@
     return true;
 
   const URLPatternSet& old_list = effective_hosts();
   const URLPatternSet& new_list = permissions->effective_hosts();
 
   // TODO(jstritar): This is overly conservative with respect to subdomains.
   // For example, going from *.google.com to www.google.com will be
   // considered an elevation, even though it is not (http://crbug.com/65337).
   std::set<std::string> new_hosts_set(GetDistinctHosts(new_list, false, false));
   std::set<std::string> old_hosts_set(GetDistinctHosts(old_list, false, false));
-  std::set<std::string> new_hosts_only;
-
-  std::set_difference(new_hosts_set.begin(), new_hosts_set.end(),
-                      old_hosts_set.begin(), old_hosts_set.end(),
-                      std::inserter(new_hosts_only, new_hosts_only.begin()));
+  std::set<std::string> new_hosts_only =
+      base::STLSetDifference<std::set<std::string> >(new_hosts_set,
+                                                     old_hosts_set);
 
   return !new_hosts_only.empty();
 }
 
 }  // namespace extensions