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

chrome/browser/extensions/external_policy_loader_unittest.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 <set>
 #include <string>
 
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/values.h"
@@ skipping 121 matching lines @@
   base::DictionaryValue forced_extensions;
   std::set<std::string> expected_extensions;
 
   extensions::ExternalPolicyLoader::AddExtension(
       &forced_extensions, "cccccccccccccccccccccccccccccccc",
       "http://www.example.com/crx");
   expected_extensions.insert("cccccccccccccccccccccccccccccccc");
 
   // Add invalid entries.
   forced_extensions.SetString("invalid", "http://www.example.com/crx");
-  forced_extensions.SetString("dddddddddddddddddddddddddddddddd", "");
+  forced_extensions.SetString("dddddddddddddddddddddddddddddddd",
+                              std::string());
   forced_extensions.SetString("invalid", "bad");
 
   MockExternalPolicyProviderVisitor mv;
   mv.Visit(forced_extensions, expected_extensions);
 }
 
 }  // namespace extensions