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

net/tools/quic/test_tools/quic_test_client.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 "net/tools/quic/test_tools/quic_test_client.h"
 
 #include "net/tools/flip_server/balsa_headers.h"
 #include "net/tools/quic/test_tools/http_message_test_utils.h"
 
 using std::string;
@@ skipping 67 matching lines @@
 string QuicTestClient::SendCustomSynchronousRequest(
     const HTTPMessage& message) {
   SendMessage(message);
   WaitForResponse();
   return response_;
 }
 
 string QuicTestClient::SendSynchronousRequest(const string& uri) {
   if (SendRequest(uri) == 0) {
     DLOG(ERROR) << "Failed to the request for uri:" << uri;
-    return "";
+    return std::string();
   }
   WaitForResponse();
   return response_;
 }
 
 QuicReliableClientStream* QuicTestClient::GetOrCreateStream() {
   if (never_connected_ == true) {
     if (!connected()) {
       Connect();
     }
@@ skipping 75 matching lines @@
   stream_error_ = stream_->stream_error();
   connection_error_ = stream_->connection_error();
   bytes_read_ = stream_->stream_bytes_read();
   bytes_written_ = stream_->stream_bytes_written();
   stream_ = NULL;
 }
 
 }  // namespace test
 }  // namespace tools
 }  // namespace net