Add GN variables for controlling header checking.

tools/gn/setup.cc

 // 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.
 
 #include "tools/gn/setup.h"
 
 #include <stdlib.h>
 
 #include <algorithm>
 #include <sstream>
@@ skipping 172 matching lines @@
       // TODO(brettw) implement a system of warnings. Until we have a better
       // system, print the error but don't return failure.
       err.PrintToStdout();
       return true;
     }
   }
 
   if (check_public_headers_) {
     if (!commands::CheckPublicHeaders(&build_settings_,
                                       builder_->GetAllResolvedTargets(),
-                                      std::vector<const Target*>())) {
+                                      std::vector<const Target*>(),
+                                      false)) {
       return false;
     }
   }
 
   // Write out tracing and timing if requested.
   const CommandLine* cmdline = CommandLine::ForCurrentProcess();
   if (cmdline->HasSwitch(kTimeSwitch))
     PrintLongHelp(SummarizeTraces());
   if (cmdline->HasSwitch(kTracelogSwitch))
     SaveTraces(cmdline->GetSwitchValuePath(kTracelogSwitch));
@@ skipping 384 matching lines @@
 }
 
 void DependentSetup::RunPreMessageLoop() {
   CommonSetup::RunPreMessageLoop();
 }
 
 bool DependentSetup::RunPostMessageLoop() {
   return CommonSetup::RunPostMessageLoop();
 }