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

chrome/browser/extensions/api/cryptotoken_private/cryptotoken_private_api_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 "chrome/browser/extensions/api/cryptotoken_private/cryptotoken_private_api.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 27 matching lines @@
       return false;
     }
 
     if (!result_list->GetBoolean(0, result)) {
       LOG(ERROR) << "Result is not boolean.";
       return false;
     }
     return true;
   }
 
-  bool GetCanOriginAssertAppIdResult(std::string origin, std::string appId) {
+  bool GetCanOriginAssertAppIdResult(const std::string& origin,
+                                     const std::string& appId) {
     scoped_refptr<api::CryptotokenPrivateCanOriginAssertAppIdFunction> function(
         new api::CryptotokenPrivateCanOriginAssertAppIdFunction());
     function->set_has_callback(true);
 
     scoped_ptr<base::ListValue> args(new base::ListValue);
     args->AppendString(origin);
     args->AppendString(appId);
 
     extension_function_test_utils::RunFunction(
         function.get(),
@@ skipping 27 matching lines @@
   std::string gstatic_appid("https://www.gstatic.com/securitykey/origins.json");
   EXPECT_TRUE(GetCanOriginAssertAppIdResult(google_origin, gstatic_appid));
   // Not all gstatic urls are allowed, just those specifically whitelisted.
   std::string gstatic_otherurl("https://www.gstatic.com/foobar");
   EXPECT_FALSE(GetCanOriginAssertAppIdResult(google_origin, gstatic_otherurl));
 }
 
 }  // namespace
 
 }  // namespace extensions