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

net/http/http_cache_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 "net/http/http_cache.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
@@ skipping 445 matching lines @@
     0,
     0,
     OK};
 
 const char kFullRangeData[] =
     "rg: 00-09 rg: 10-19 rg: 20-29 rg: 30-39 "
     "rg: 40-49 rg: 50-59 rg: 60-69 rg: 70-79 ";
 
 // Verifies the response headers (|response|) match a partial content
 // response for the range starting at |start| and ending at |end|.
-void Verify206Response(std::string response, int start, int end) {
+void Verify206Response(const std::string& response, int start, int end) {
   std::string raw_headers(
       HttpUtil::AssembleRawHeaders(response.data(), response.size()));
   scoped_refptr<HttpResponseHeaders> headers(
       new HttpResponseHeaders(raw_headers));
 
   ASSERT_EQ(206, headers->response_code());
 
   int64 range_start, range_end, object_size;
   ASSERT_TRUE(
       headers->GetContentRange(&range_start, &range_end, &object_size));
@@ skipping 7215 matching lines @@
   EXPECT_EQ(1, cache.disk_cache()->open_count());
   EXPECT_EQ(1, cache.disk_cache()->create_count());
   EXPECT_TRUE(response_info.was_cached);
 
   // The new SSL state is reported.
   EXPECT_EQ(status2, response_info.ssl_info.connection_status);
   EXPECT_TRUE(cert2->Equals(response_info.ssl_info.cert.get()));
 }
 
 }  // namespace net