Add GN variables for controlling header checking.

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>
@@ skipping 81 matching lines @@
 bool ResolveTargetsFromCommandLinePattern(
     Setup* setup,
     const std::string& label_pattern,
     bool all_toolchains,
     std::vector<const Target*>* matches);
 
 // Runs the header checker. All targets in the build should be given in
 // all_targets, and the specific targets to check should be in to_check. If
 // to_check is empty, all targets will be checked.
 //
+// force_check, if true, will override targets opting out of header checking
+// with "check_includes = false" and will check them anyway.
+//
 // On success, returns true. If the check fails, the error(s) will be printed
 // to stdout and false will be returned.
 bool CheckPublicHeaders(const BuildSettings* build_settings,
                         const std::vector<const Target*>& all_targets,
-                        const std::vector<const Target*>& to_check);
+                        const std::vector<const Target*>& to_check,
+                        bool force_check);
 
 }  // namespace commands
 
 #endif  // TOOLS_GN_COMMANDS_H_