Add optional public header checking to GN build

tools/gn/commands.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_COMMANDS_H_
 #define TOOLS_GN_COMMANDS_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/strings/string_piece.h"
 
 class Target;
 
 // Each "Run" command returns the value we should return from main().
 
 namespace commands {
 
 typedef int (*CommandRunner)(const std::vector<std::string>&);
 
 extern const char kArgs[];
 extern const char kArgs_HelpShort[];
 extern const char kArgs_Help[];
 int RunArgs(const std::vector<std::string>& args);
 
+extern const char kCheck[];
+extern const char kCheck_HelpShort[];
+extern const char kCheck_Help[];
+int RunCheck(const std::vector<std::string>& args);
+
 extern const char kDesc[];
 extern const char kDesc_HelpShort[];
 extern const char kDesc_Help[];
 int RunDesc(const std::vector<std::string>& args);
 
 extern const char kGen[];
 extern const char kGen_HelpShort[];
 extern const char kGen_Help[];
 int RunGen(const std::vector<std::string>& args);
 
@@ skipping 31 matching lines @@
 //
 // Note that a lot of memory is leaked to avoid proper teardown under the
 // assumption that you will only run this once and exit.
 //
 // On failure, prints an error message and returns NULL.
 const Target* GetTargetForDesc(const std::vector<std::string>& args);
 
 }  // namespace commands
 
 #endif  // TOOLS_GN_COMMANDS_H_