Move WriteFile and WriteFileDescriptor from file_util to base namespace.

chrome/utility/extensions/unpacker.cc

Index: chrome/utility/extensions/unpacker.cc
diff --git a/chrome/utility/extensions/unpacker.cc b/chrome/utility/extensions/unpacker.cc
index f056fc34363fc079da733021c563861ad842b849..1d74788960a37e962658b8038a41bc65221928e9 100644
--- a/chrome/utility/extensions/unpacker.cc
+++ b/chrome/utility/extensions/unpacker.cc
@@ -88,7 +88,7 @@ bool PathContainsParentDirectory(const base::FilePath& path) {
 bool WritePickle(const IPC::Message& pickle, const base::FilePath& dest_path) {
   int size = base::checked_cast<int>(pickle.size());
   const char* data = static_cast<const char*>(pickle.data());
-  int bytes_written = file_util::WriteFile(dest_path, data, size);
+  int bytes_written = base::WriteFile(dest_path, data, size);
   return (bytes_written == size);
 }