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

sync/notifier/sync_invalidation_listener_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 <cstddef>
 #include <set>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/message_loop.h"
@@ skipping 130 matching lines @@
         state_(TRANSIENT_INVALIDATION_ERROR) {}
   virtual ~FakeDelegate() {}
 
   int GetInvalidationCount(const ObjectId& id) const {
     ObjectIdCountMap::const_iterator it = invalidation_counts_.find(id);
     return (it == invalidation_counts_.end()) ? 0 : it->second;
   }
 
   std::string GetPayload(const ObjectId& id) const {
     ObjectIdInvalidationMap::const_iterator it = invalidations_.find(id);
-    return (it == invalidations_.end()) ? "" : it->second.payload;
+    return (it == invalidations_.end()) ? std::string() : it->second.payload;
   }
 
   InvalidatorState GetInvalidatorState() const {
     return state_;
   }
 
   void Acknowledge(const ObjectId& id) {
     listener_->Acknowledge(id, invalidations_[id].ack_handle);
   }
 
@@ skipping 793 matching lines @@
   EXPECT_EQ(INVALIDATION_CREDENTIALS_REJECTED, GetInvalidatorState());
 
   listener_.Ready(fake_invalidation_client_);
 
   EXPECT_EQ(INVALIDATIONS_ENABLED, GetInvalidatorState());
 }
 
 }  // namespace
 
 }  // namespace syncer