Move WriteFile and WriteFileDescriptor from file_util to base namespace.

net/http/http_network_transaction_unittest.cc

Index: net/http/http_network_transaction_unittest.cc
diff --git a/net/http/http_network_transaction_unittest.cc b/net/http/http_network_transaction_unittest.cc
index e4edbb9aa8fb799fd7b21791ba557fe6ef49ba94..aa7967d81fc754d2699a45bbee12201f27e52a92 100644
--- a/net/http/http_network_transaction_unittest.cc
+++ b/net/http/http_network_transaction_unittest.cc
@@ -7861,7 +7861,7 @@ TEST_P(HttpNetworkTransactionTest, UploadUnreadableFile) {
   base::FilePath temp_file;
   ASSERT_TRUE(base::CreateTemporaryFile(&temp_file));
   std::string temp_file_content("Unreadable file.");
-  ASSERT_TRUE(file_util::WriteFile(temp_file, temp_file_content.c_str(),
+  ASSERT_TRUE(base::WriteFile(temp_file, temp_file_content.c_str(),
                                    temp_file_content.length()));
   ASSERT_TRUE(file_util::MakeFileUnreadable(temp_file));