Move WriteFile and WriteFileDescriptor from file_util to base namespace.

chromeos/dbus/session_manager_client.cc

Index: chromeos/dbus/session_manager_client.cc
diff --git a/chromeos/dbus/session_manager_client.cc b/chromeos/dbus/session_manager_client.cc
index c01f28f759002025b96366e910dc75f74e3c946b..737a9be3786463fd6e0d8995fdb76e3a240d56af 100644
--- a/chromeos/dbus/session_manager_client.cc
+++ b/chromeos/dbus/session_manager_client.cc
@@ -611,7 +611,7 @@ class SessionManagerClientStubImpl : public SessionManagerClient {
                                     const std::string& data) {
     const int size = static_cast<int>(data.size());
     if (!base::CreateDirectory(path.DirName()) ||
-        file_util::WriteFile(path, data.data(), size) != size) {
+        base::WriteFile(path, data.data(), size) != size) {
       LOG(WARNING) << "Failed to write policy key to " << path.value();
     }
   }