Rewrite std::string("") to std::string(), Linux edition.

chrome/common/extensions/features/permission_feature.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 "chrome/common/extensions/features/permission_feature.h"
 
 #include "chrome/common/extensions/permissions/permission_set.h"
 
 namespace extensions {
 
@@ skipping 31 matching lines @@
     return error;
 
   if (extension_types()->empty()) {
     return name() + ": Permission features must specify at least one " +
         "value for extension_types.";
   }
 
   if (!GetContexts()->empty())
     return name() + ": Permission features do not support contexts.";
 
-  return "";
+  return std::string();
 }
 
 }  // namespace