Add optional public header checking to GN build

tools/gn/target.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/target.h"
 
 #include "base/bind.h"
 #include "tools/gn/config_values_extractors.h"
 #include "tools/gn/scheduler.h"
 
@@ skipping 36 matching lines @@
       unique_configs->insert(all[i].ptr);
     }
   }
 }
 
 }  // namespace
 
 Target::Target(const Settings* settings, const Label& label)
     : Item(settings, label),
       output_type_(UNKNOWN),
+      all_headers_public_(true),
       hard_dep_(false) {
 }
 
 Target::~Target() {
 }
 
 // static
 const char* Target::GetStringForOutputType(OutputType type) {
   switch (type) {
     case UNKNOWN:
@@ skipping 122 matching lines @@
     // don't need to bother copying to our configs, only forwarding.
     DCHECK(std::find_if(deps_.begin(), deps_.end(),
                         LabelPtrPtrEquals<Target>(from_target)) !=
            deps_.end());
     direct_dependent_configs_.insert(
         direct_dependent_configs_.end(),
         from_target->direct_dependent_configs().begin(),
         from_target->direct_dependent_configs().end());
   }
 }