Move WriteFile and WriteFileDescriptor from file_util to base namespace.

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/file_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ skipping 59 matching lines @@
   // Write file, creating the directory if necessary.
   base::FilePath file_path =
       scope->settings()->build_settings()->GetFullPath(source_file);
   const std::string& contents_string = contents.str();
   if (!base::CreateDirectory(file_path.DirName())) {
     *err = Err(function->function(), "Unable to create directory.",
                "I was using \"" + FilePathToUTF8(file_path.DirName()) + "\".");
     return Value();
   }
   int int_size = static_cast<int>(contents_string.size());
-  if (file_util::WriteFile(file_path, contents_string.c_str(), int_size)
+  if (base::WriteFile(file_path, contents_string.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