Cleanup: Pass std::string as const reference from tools/clang/

tools/clang/empty_string/tests/test-original.cc

 // Copyright (c) 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.
 //
 // Test file for the empty string clang tool.
 
 #include <string>
 
 // Tests for std::string declarations.
 void TestDeclarations() { std::string a(""), b("abc"), c(""); }
@@ skipping 14 matching lines @@
   TestInitializers(double) : a(""), b("cat"), c() {}
 
  private:
   std::string a;
   std::string b;
   std::string c;
 };
 
 // Tests for temporary std::strings.
 void TestTemporaries(const std::string& reference_argument,
-                     const std::string value_argument) {
+                     const std::string& value_argument) {

[hans, 2016/05/25 17:31:25]

This file is a test case for the plugin, it's not actually code that we run, so
it shouldn't be changed.

Also note that the name of this parameter suggests it should be passed by value
rather than reference :-)

[ki.stfu, 2016/05/25 17:37:58]

Thanks for very quick response!

   TestTemporaries("", "");
   TestTemporaries(std::string(""), std::string(""));
 }
 
 // Tests for temporary std::wstrings.
 void TestWideTemporaries(const std::wstring& reference_argument,
-                         const std::wstring value_argument) {
+                         const std::wstring& value_argument) {
   TestWideTemporaries(L"", L"");
   TestWideTemporaries(std::wstring(L""), std::wstring(L""));
 }