Refactor GN source expansions.

tools/gn/substitution_list.h

+// Copyright 2014 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_SUBSTUTITION_LIST_H
+#define TOOLS_GN_SUBSTUTITION_LIST_H
+
+#include <string>
+#include <vector>
+
+#include "tools/gn/substitution_pattern.h"
+
+// Represents a list of strings with {{substitution_patterns}} in them.
+class SubstitutionList {
+ public:
+  SubstitutionList();
+  ~SubstitutionList();
+
+  bool Parse(const Value& value, Err* err);
+  bool Parse(const std::vector<std::string>& values,
+             const ParseNode* origin,
+             Err* err);
+
+  // Makes a SubstitutionList from the given hardcoded patterns.
+  static SubstitutionList MakeForTest(
+      const char* a,
+      const char* b = NULL,
+      const char* c = NULL);
+
+  const std::vector<SubstitutionPattern>& list() const { return list_; }
+
+  // Returns a list of all substitution types used by the patterns in thist
+  // list, with the exception of LITERAL.
+  const std::vector<SubstitutionType>& required_types() const {
+    return required_types_;
+  }
+
+ private:
+  void FillRequiredTypes();
+
+  std::vector<SubstitutionPattern> list_;
+
+  std::vector<SubstitutionType> required_types_;
+};
+
+#endif  // TOOLS_GN_SUBSTUTITION_LIST_H