Move WriteFile and WriteFileDescriptor from file_util to base namespace.

chromeos/dbus/cros_disks_client.cc

Index: chromeos/dbus/cros_disks_client.cc
diff --git a/chromeos/dbus/cros_disks_client.cc b/chromeos/dbus/cros_disks_client.cc
index d841959ac1bbaa5c89cf021abc4d95e46b97fb01..fae607db8c3164af7e083383853558af9f69cd93 100644
--- a/chromeos/dbus/cros_disks_client.cc
+++ b/chromeos/dbus/cros_disks_client.cc
@@ -485,7 +485,7 @@ class CrosDisksClientStubImpl : public CrosDisksClient {
     const base::FilePath dummy_file_path =
         mounted_path.Append("SUCCESSFULLY_PERFORMED_FAKE_MOUNT.txt");
     const std::string dummy_file_content = "This is a dummy file.";
-    const int write_result = file_util::WriteFile(
+    const int write_result = base::WriteFile(
         dummy_file_path, dummy_file_content.data(), dummy_file_content.size());
     if (write_result != static_cast<int>(dummy_file_content.size())) {
       DLOG(ERROR) << "Failed to put a dummy file at "