Move WriteFile and WriteFileDescriptor from file_util to base namespace.

content/public/test/async_file_test_helper.cc

Index: content/public/test/async_file_test_helper.cc
diff --git a/content/public/test/async_file_test_helper.cc b/content/public/test/async_file_test_helper.cc
index 2da0bf8d1153c8f480cd6a4302c925534eb39628..03376f9b969cc453c69b7fb491f2a329c7853da0 100644
--- a/content/public/test/async_file_test_helper.cc
+++ b/content/public/test/async_file_test_helper.cc
@@ -181,7 +181,7 @@ base::File::Error AsyncFileTestHelper::CreateFileWithData(
   if (!dir.CreateUniqueTempDir())
     return base::File::FILE_ERROR_FAILED;
   base::FilePath local_path = dir.path().AppendASCII("tmp");
-  if (buf_size != file_util::WriteFile(local_path, buf, buf_size))
+  if (buf_size != base::WriteFile(local_path, buf, buf_size))
     return base::File::FILE_ERROR_FAILED;
   base::File::Error result = base::File::FILE_ERROR_FAILED;
   base::RunLoop run_loop;