Add output reference to gen written files.

tools/gn/function_write_file.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 <iostream>
 #include <sstream>
 
 #include "base/files/file_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ skipping 97 matching lines @@
   SourceFile source_file = cur_dir.ResolveRelativeFile(args[0], err,
       scope->settings()->build_settings()->root_path_utf8());
   if (err->has_error())
     return Value();
   if (!EnsureStringIsInOutputDir(
           scope->settings()->build_settings()->build_dir(),
           source_file.value(), args[0].origin(), err))
     return Value();
   g_scheduler->AddWrittenFile(source_file);  // Track that we wrote this file.
 
-  // Track how to recreate this file, since we write it a gen time.
-  // Note this is a hack since the correct output is not a dependency proper,
-  // but an addition of this file to the output of the gn rule that writes it.
-  // This dependency will, however, cause the gen step to be re-run and the
-  // build restarted if the file is missing.
-  g_scheduler->AddGenDependency(
-      scope->settings()->build_settings()->GetFullPath(source_file));
-
   // Compute output.
   std::ostringstream contents;
   if (args[1].type() == Value::LIST) {
     const std::vector<Value>& list = args[1].list_value();
     for (const auto& cur : list)
       contents << cur.ToString(false) << std::endl;
   } else {
     contents << args[1].ToString(false);
   }
   const std::string& new_contents = contents.str();
@@ skipping 17 matching lines @@
   if (DoWriteFile(file_path, new_contents.c_str(), int_size)
       != int_size) {
     *err = Err(function->function(), "Unable to write file.",
                "I was writing \"" + FilePathToUTF8(file_path) + "\".");
     return Value();
   }
   return Value();
 }
 
 }  // namespace functions