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

net/tools/flip_server/streamer_interface.h

 // Copyright (c) 2011 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_FLIP_SERVER_STREAMER_INTERFACE_H_
 #define NET_TOOLS_FLIP_SERVER_STREAMER_INTERFACE_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 39 matching lines @@
   void Reset() override;
   void ResetForNewInterface(int32 server_idx) override {}
   void ResetForNewConnection() override;
   void Cleanup() override;
   int PostAcceptHook() override;
   void NewStream(uint32 stream_id,
                  uint32 priority,
                  const std::string& filename) override {}
   void SendEOF(uint32 stream_id) override {}
   void SendErrorNotFound(uint32 stream_id) override {}
-  virtual void SendOKResponse(uint32 stream_id, std::string output) {}
+  virtual void SendOKResponse(uint32 stream_id, const std::string& output) {}
   size_t SendSynStream(uint32 stream_id, const BalsaHeaders& headers) override;
   size_t SendSynReply(uint32 stream_id, const BalsaHeaders& headers) override;
   void SendDataFrame(uint32 stream_id,
                      const char* data,
                      int64 len,
                      uint32 flags,
                      bool compress) override {}
   void set_is_request() override;
   static std::string forward_ip_header() { return forward_ip_header_; }
-  static void set_forward_ip_header(std::string value) {
+  static void set_forward_ip_header(const std::string& value) {
     forward_ip_header_ = value;
   }
 
  private:
   void SendEOFImpl(uint32 stream_id) {}
   void SendErrorNotFoundImpl(uint32 stream_id) {}
   void SendOKResponseImpl(uint32 stream_id, std::string* output) {}
   size_t SendSynReplyImpl(uint32 stream_id, const BalsaHeaders& headers) {
     return 0;
   }
@@ skipping 44 matching lines @@
   FlipAcceptor* acceptor_;
   bool is_request_;
   BalsaFrame* http_framer_;
   BalsaHeaders headers_;
   static std::string forward_ip_header_;
 };
 
 }  // namespace net
 
 #endif  // NET_TOOLS_FLIP_SERVER_STREAMER_INTERFACE_H_