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

sync/notifier/push_client_channel_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 "sync/notifier/push_client_channel.h"
 
 #include <cstddef>
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 55 matching lines @@
   EXPECT_EQ(kServiceContext, service_context);
   EXPECT_EQ(kSchedulingHash, scheduling_hash);
 }
 
 // Encode a message with no context into a notification and then
 // decode it.  The decoded message should match the original message,
 // but the context and hash should be untouched.
 TEST_F(PushClientChannelTest, EncodeDecodeNoContext) {
   const notifier::Notification& notification =
       PushClientChannel::EncodeMessageForTest(
-          kMessage, "", kSchedulingHash);
+          kMessage, std::string(), kSchedulingHash);
   std::string message;
   std::string service_context = kServiceContext;
   int64 scheduling_hash = kSchedulingHash + 1;
   EXPECT_TRUE(PushClientChannel::DecodeMessageForTest(
       notification, &message, &service_context, &scheduling_hash));
   EXPECT_EQ(kMessage, message);
   EXPECT_EQ(kServiceContext, service_context);
   EXPECT_EQ(kSchedulingHash + 1, scheduling_hash);
 }
 
@@ skipping 157 matching lines @@
         fake_push_client_->sent_notifications()[1],
         &message, &service_context, &scheduling_hash));
     EXPECT_EQ(kMessage, message);
     EXPECT_EQ(kServiceContext, service_context);
     EXPECT_EQ(kSchedulingHash, scheduling_hash);
   }
 }
 
 }  // namespace
 }  // namespace syncer