Add initial prototype for the GN meta-buildsystem.

tools/gn/config.h

Index: tools/gn/config.h
diff --git a/tools/gn/config.h b/tools/gn/config.h
new file mode 100644
index 0000000000000000000000000000000000000000..0ee9b7ba36ace940284716165d5ed5a51ad0c0e0
--- /dev/null
+++ b/tools/gn/config.h
@@ -0,0 +1,45 @@
+// 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_CONFIG_H_
+#define TOOLS_GN_CONFIG_H_
+
+#include "base/compiler_specific.h"
+#include "tools/gn/config_values.h"
+#include "tools/gn/item.h"
+
+class Err;
+class ItemTree;
+class LocationRange;
+class Settings;
+
+// Represents a named config in the dependency graph.
+class Config : public Item {
+ public:
+  Config(const Label& label);
+  virtual ~Config();
+
+  virtual Config* AsConfig() OVERRIDE;
+  virtual const Config* AsConfig() const OVERRIDE;
+
+  ConfigValues& config_values() { return config_values_; }
+  const ConfigValues& config_values() const { return config_values_; }
+
+  // Gets or creates a config.
+  //
+  // This is like the TargetManager is for Targets, but Configs are so much
+  // simpler that this one function is all we need.
+  static Config* GetConfig(const Settings* settings,
+                           const LocationRange& specified_from_here,
+                           const Label& label,
+                           Item* dep_from,
+                           Err* err);
+
+ private:
+  ConfigValues config_values_;
+
+  DISALLOW_COPY_AND_ASSIGN(Config);
+};
+
+#endif  // TOOLS_GN_CONFIG_H_