Add initial prototype for the GN meta-buildsystem.

tools/gn/operators.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_OPERATORS_H_
+#define TOOLS_GN_OPERATORS_H_
+
+class BinaryOpNode;
+class Err;
+class ParseNode;
+class Scope;
+class Token;
+class UnaryOpNode;
+class Value;
+
+bool IsUnaryOperator(const Token& token);
+bool IsBinaryOperator(const Token& token);
+
+bool IsFunctionCallArgBeginScoper(const Token& token);  // "("
+bool IsFunctionCallArgEndScoper(const Token& token);  // ")"
+
+bool IsScopeBeginScoper(const Token& token);  // "{"
+bool IsScopeEndScoper(const Token& token);  // "}"
+
+Value ExecuteUnaryOperator(Scope* scope,
+                           const UnaryOpNode* op_node,
+                           const Value& value,
+                           Err* err);
+Value ExecuteBinaryOperator(Scope* scope,
+                            const BinaryOpNode* op_node,
+                            const ParseNode* left,
+                            const ParseNode* right,
+                            Err* err);
+
+#endif  // TOOLS_GN_OPERATORS_H_