Allow creation and modification of scopes in GN.

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 <stddef.h>
 #include <utility>
 
 #include "base/strings/string_number_conversions.h"
@@ skipping 55 matching lines @@
     : type_(other.type_),
       string_value_(other.string_value_),
       boolean_value_(other.boolean_value_),
       int_value_(other.int_value_),
       list_value_(other.list_value_),
       origin_(other.origin_) {
   if (type() == SCOPE && other.scope_value_.get())
     scope_value_ = other.scope_value_->MakeClosure();
 }
 
+Value::Value(Value&& other) = default;
+
 Value::~Value() {
 }
 
 Value& Value::operator=(const Value& other) {
   type_ = other.type_;
   string_value_ = other.string_value_;
   boolean_value_ = other.boolean_value_;
   int_value_ = other.int_value_;
   list_value_ = other.list_value_;
   if (type() == SCOPE && other.scope_value_.get())
@@ skipping 126 matching lines @@
       // iteration code.
       return false;
     default:
       return false;
   }
 }
 
 bool Value::operator!=(const Value& other) const {
   return !operator==(other);
 }