Add initial prototype for the GN meta-buildsystem.

tools/gn/commands.h

Index: tools/gn/commands.h
diff --git a/tools/gn/commands.h b/tools/gn/commands.h
new file mode 100644
index 0000000000000000000000000000000000000000..1d4449cc1c9d7e8865283f5c8f7b7c7121c73d41
--- /dev/null
+++ b/tools/gn/commands.h
@@ -0,0 +1,18 @@
+// 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_COMMANDS_H_
+#define TOOLS_GN_COMMANDS_H_
+
+#include <string>
+#include <vector>
+
+// The different commands we have, returns the value we should return from
+// main().
+int RunDepsCommand(const std::vector<std::string>& args);
+int RunDescCommand(const std::vector<std::string>& args);
+int RunGenCommand(const std::vector<std::string>& args);
+int RunTreeCommand(const std::vector<std::string>& args);
+
+#endif  // TOOLS_GN_COMMANDS_H_