Cleanup: Initialize Value from tools/gn by moving std::string

tools/gn/value.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.
 
 #include "tools/gn/value.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/scope.h"
 
@@ skipping 18 matching lines @@
       origin_(origin) {
 }
 
 Value::Value(const ParseNode* origin, int64_t int_val)
     : type_(INTEGER),
       boolean_value_(false),
       int_value_(int_val),
       origin_(origin) {
 }
 
-Value::Value(const ParseNode* origin, std::string str_val)
+Value::Value(const ParseNode* origin, const std::string& str_val)
     : type_(STRING),
-      string_value_(),
+      string_value_(str_val),
       boolean_value_(false),
       int_value_(0),
       origin_(origin) {
-  string_value_.swap(str_val);
 }
 
 Value::Value(const ParseNode* origin, const char* str_val)
     : type_(STRING),
       string_value_(str_val),
       boolean_value_(false),
       int_value_(0),
       origin_(origin) {
 }
 
@@ skipping 156 matching lines @@
       // iteration code.
       return false;
     default:
       return false;
   }
 }
 
 bool Value::operator!=(const Value& other) const {
   return !operator==(other);
 }