Cleanup: Pass std::string as const reference if possible

net/tools/quic/test_tools/quic_test_client.h

 // 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.
 
 #ifndef NET_TOOLS_QUIC_TEST_TOOLS_QUIC_TEST_CLIENT_H_
 #define NET_TOOLS_QUIC_TEST_TOOLS_QUIC_TEST_CLIENT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 71 matching lines @@
 
   // ExpectCertificates controls whether the server is expected to provide
   // certificates. The certificates, if any, are not verified, but the common
   // name is recorded and available with |cert_common_name()|.
   void ExpectCertificates(bool on);
 
   // Sets the |user_agent_id| of the |client_|.
   void SetUserAgentID(const std::string& user_agent_id);
 
   // Wraps data in a quic packet and sends it.
-  ssize_t SendData(std::string data, bool last_data);
+  ssize_t SendData(const std::string& data, bool last_data);
   // As above, but |delegate| will be notified when |data| is ACKed.
-  ssize_t SendData(std::string data,
+  ssize_t SendData(const std::string& data,
                    bool last_data,
                    QuicAckNotifier::DelegateInterface* delegate);
 
   // From SimpleClient
   // Clears any outstanding state and sends a simple GET of 'uri' to the
   // server.  Returns 0 if the request failed and no bytes were written.
   ssize_t SendRequest(const std::string& uri) override;
   // Sends requests for all the urls and waits for the responses.  To process
   // the individual responses as they are returned, the caller should use the
   // set the response_listener on the client().
@@ skipping 145 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(QuicTestClient);
 };
 
 }  // namespace test
 
 }  // namespace tools
 }  // namespace net
 
 #endif  // NET_TOOLS_QUIC_TEST_TOOLS_QUIC_TEST_CLIENT_H_