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

components/search_engines/template_url_parser_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 "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/common/chrome_paths.h"
 #include "components/search_engines/search_terms_data.h"
 #include "components/search_engines/template_url.h"
 #include "components/search_engines/template_url_parser.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using base::ASCIIToUTF16;
 
 // ParamFilterImpl ------------------------------------------------------------
 
 // Filters any param which as an occurrence of name_str_ in its name or an
 // occurrence of value_str_ in its value.
 class ParamFilterImpl : public TemplateURLParser::ParameterFilter {
  public:
-  ParamFilterImpl(std::string name_str, std::string value_str);
+  ParamFilterImpl(const std::string& name_str, const std::string& value_str);
   ~ParamFilterImpl() override;
 
   bool KeepParameter(const std::string& key, const std::string& value) override;
 
  private:
   std::string name_str_;
   std::string value_str_;
 
   DISALLOW_COPY_AND_ASSIGN(ParamFilterImpl);
 };
 
-ParamFilterImpl::ParamFilterImpl(std::string name_str, std::string value_str)
-   : name_str_(name_str),
-     value_str_(value_str) {
-}
+ParamFilterImpl::ParamFilterImpl(const std::string& name_str,
+                                 const std::string& value_str)
+    : name_str_(name_str), value_str_(value_str) {}
 
 ParamFilterImpl::~ParamFilterImpl() {
 }
 
 bool ParamFilterImpl::KeepParameter(const std::string& key,
                                     const std::string& value) {
   return (name_str_.empty() || key.find(name_str_) == std::string::npos) &&
          (value_str_.empty() || value.find(value_str_) == std::string::npos);
 }
 
@@ skipping 204 matching lines @@
   EXPECT_EQ(ASCIIToUTF16("Yahoo"), template_url_->short_name());
   EXPECT_TRUE(template_url_->url_ref().SupportsReplacement(SearchTermsData()));
   EXPECT_TRUE(template_url_->suggestions_url().empty());
   EXPECT_EQ("http://search.yahoo.com/search?p={searchTerms}&ei=UTF-8",
             template_url_->url());
   ASSERT_EQ(1U, template_url_->input_encodings().size());
   EXPECT_EQ("UTF-8", template_url_->input_encodings()[0]);
   EXPECT_EQ(GURL("http://search.yahoo.com/favicon.ico"),
             template_url_->favicon_url());
 }