Move WriteFile and WriteFileDescriptor from file_util to base namespace.

courgette/third_party/bsdiff_apply.cc

Index: courgette/third_party/bsdiff_apply.cc
diff --git a/courgette/third_party/bsdiff_apply.cc b/courgette/third_party/bsdiff_apply.cc
index 3ed346e79af925d0fbcd941d922337f7774127a2..435acc09355b7c154bcecb0986d83d64192e4848 100644
--- a/courgette/third_party/bsdiff_apply.cc
+++ b/courgette/third_party/bsdiff_apply.cc
@@ -200,7 +200,7 @@ BSDiffStatus ApplyBinaryPatch(const base::FilePath& old_file_path,
   }
 
   // Write the stream to disk.
-  int written = file_util::WriteFile(
+  int written = base::WriteFile(
       new_file_path,
       reinterpret_cast<const char*>(new_sink_stream.Buffer()),
       static_cast<int>(new_sink_stream.Length()));