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

sync/engine/syncer_util.cc

 // Copyright 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 "sync/engine/syncer_util.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 615 matching lines @@
   // removed entirely (if this type of undeletion is indeed impossible).
   CHECK(target->good());
   DVLOG(1) << "Server update is attempting undelete. " << *target
            << "Update:" << SyncerProtoUtil::SyncEntityDebugString(update);
   // Move the old one aside and start over.  It's too tricky to get the old one
   // back into a state that would pass CheckTreeInvariants().
   if (target->Get(IS_DEL)) {
     DCHECK(target->Get(UNIQUE_CLIENT_TAG).empty())
         << "Doing move-aside undeletion on client-tagged item.";
     target->Put(ID, trans->directory()->NextId());
-    target->Put(UNIQUE_CLIENT_TAG, "");
+    target->Put(UNIQUE_CLIENT_TAG, std::string());
     target->Put(BASE_VERSION, CHANGES_VERSION);
     target->Put(SERVER_VERSION, 0);
     return VERIFY_SUCCESS;
   }
   if (update.version() < target->Get(SERVER_VERSION)) {
     LOG(WARNING) << "Update older than current server version for "
                  << *target << " Update:"
                  << SyncerProtoUtil::SyncEntityDebugString(update);
     return VERIFY_SUCCESS;  // Expected in new sync protocol.
   }
   return VERIFY_UNDECIDED;
 }
 
 }  // namespace syncer