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

chrome/browser/local_discovery/privet_url_fetcher_unittest.cc

 // Copyright 2013 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 "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "chrome/browser/local_discovery/privet_url_fetcher.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "net/url_request/url_request_test_util.h"
@@ skipping 53 matching lines @@
     if (response_is_file) {
       EXPECT_TRUE(response_file != base::FilePath());
       OnFileInternal();
     } else {
       OnRawDataInternal(data);
     }
 
     return true;
   }
 
-  MOCK_METHOD1(OnRawDataInternal, void(std::string data));
+  MOCK_METHOD1(OnRawDataInternal, void(const std::string& data));
 
   MOCK_METHOD0(OnFileInternal, void());
 
   const base::DictionaryValue* saved_value() { return saved_value_.get(); }
 
   void SetRawMode(bool raw_mode) {
     raw_mode_ = raw_mode;
   }
 
   std::string GetAuthToken() { return "MyAuthToken"; }
@@ skipping 230 matching lines @@
   std::string header_token;
   ASSERT_FALSE(headers.GetHeader("X-Privet-Token", &header_token));
   ASSERT_FALSE(headers.GetHeader("X-Privet-Auth", &header_token));
   ASSERT_TRUE(headers.GetHeader("Authorization", &header_token));
   ASSERT_EQ("MyAuthToken", header_token);
 }
 
 }  // namespace
 
 }  // namespace local_discovery