Add runtime dependency extraction for GN.

tools/gn/ninja_target_writer.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/ninja_target_writer.h"
 
-#include <fstream>
 #include <sstream>
 
 #include "base/files/file_util.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/ninja_action_target_writer.h"
 #include "tools/gn/ninja_binary_target_writer.h"
 #include "tools/gn/ninja_copy_target_writer.h"
 #include "tools/gn/ninja_group_target_writer.h"
@@ skipping 236 matching lines @@
        << GetNinjaRulePrefixForToolchain(settings_)
        << Toolchain::ToolTypeToName(Toolchain::TYPE_STAMP);
   path_output_.WriteFiles(out_, files);
 
   if (!order_only_deps.empty()) {
     out_ << " ||";
     path_output_.WriteFiles(out_, order_only_deps);
   }
   out_ << std::endl;
 }