Allow creation and modification of scopes in GN.

tools/gn/value.h

 // 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.
 
 #ifndef TOOLS_GN_VALUE_H_
 #define TOOLS_GN_VALUE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 25 matching lines @@
   Value(const ParseNode* origin, std::string str_val);
   Value(const ParseNode* origin, const char* str_val);
   // Values "shouldn't" have null scopes when type == Scope, so be sure to
   // always set one. However, this is not asserted since there are some
   // use-cases for creating values and immediately setting the scope on it. So
   // you can pass a null scope here if you promise to set it before any other
   // code gets it (code will generally assume the scope is not null).
   Value(const ParseNode* origin, std::unique_ptr<Scope> scope);
 
   Value(const Value& other);
+  Value(Value&& other);
   ~Value();
 
   Value& operator=(const Value& other);
+  Value& operator=(Value&& other) = default;
 
   Type type() const { return type_; }
 
   // Returns a string describing the given type.
   static const char* DescribeType(Type t);
 
   // Returns the node that made this. May be NULL.
   const ParseNode* origin() const { return origin_; }
   void set_origin(const ParseNode* o) { origin_ = o; }
 
@@ skipping 65 matching lines @@
   std::string string_value_;
   bool boolean_value_;
   int64_t int_value_;
   std::vector<Value> list_value_;
   std::unique_ptr<Scope> scope_value_;
 
   const ParseNode* origin_;
 };
 
 #endif  // TOOLS_GN_VALUE_H_