Implement target visibility in GN

tools/gn/function_toolchain.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/err.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
@@ skipping 89 matching lines @@
   // have toolchain names.
   const SourceDir& input_dir = scope->GetSourceDir();
   Label label(input_dir, args[0].string_value());
   if (g_scheduler->verbose_logging())
     g_scheduler->Log("Definining toolchain", label.GetUserVisibleName(false));
 
   // This object will actually be copied into the one owned by the toolchain
   // manager, but that has to be done in the lock.
   scoped_ptr<Toolchain> toolchain(new Toolchain(scope->settings(), label));
   toolchain->set_defined_from(function);
+  toolchain->visibility().SetPublic();
 
   Scope block_scope(scope);
   block_scope.SetProperty(&kToolchainPropertyKey, toolchain.get());
   block->ExecuteBlockInScope(&block_scope, err);
   block_scope.SetProperty(&kToolchainPropertyKey, NULL);
   if (err->has_error())
     return Value();
 
   if (!block_scope.CheckForUnusedVars(err))
     return Value();
@@ skipping 180 matching lines @@
     return Value();
 
   Scope::KeyValueMap values;
   block_scope.GetCurrentScopeValues(&values);
   toolchain->args() = values;
 
   return Value();
 }
 
 }  // namespace functions