Add optional public header checking to GN build

tools/gn/binary_target_generator.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/binary_target_generator.h"
 
 #include "tools/gn/config_values_generator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/variables.h"
@@ skipping 19 matching lines @@
     return;
 
   FillOutputExtension();
   if (err_->has_error())
     return;
 
   FillSources();
   if (err_->has_error())
     return;
 
+  FillPublic();
+  if (err_->has_error())
+    return;
+
   FillSourcePrereqs();
   if (err_->has_error())
     return;
 
   FillConfigs();
   if (err_->has_error())
     return;
 
   // Config values (compiler flags, etc.) set directly on this target.
   ConfigValuesGenerator gen(&target_->config_values(), scope_,
@@ skipping 13 matching lines @@
 }
 
 void BinaryTargetGenerator::FillOutputExtension() {
   const Value* value = scope_->GetValue(variables::kOutputExtension, true);
   if (!value)
     return;
   if (!value->VerifyTypeIs(Value::STRING, err_))
     return;
   target_->set_output_extension(value->string_value());
 }