diff -r 000000000000 -r 6474c204b198 ipc/glue/FileDescriptorUtils.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/glue/FileDescriptorUtils.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_FileDescriptorUtils_h
+#define mozilla_ipc_FileDescriptorUtils_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/FileDescriptor.h"
+#include "nsIRunnable.h"
+
+namespace mozilla {
+namespace ipc {
+
+// When Dispatch() is called (from main thread) this class arranges to close the
+// provided FileDescriptor on one of the socket transport service threads (to
+// avoid main thread I/O).
+class CloseFileRunnable MOZ_FINAL : public nsIRunnable
+{
+  typedef mozilla::ipc::FileDescriptor FileDescriptor;
+
+  FileDescriptor mFileDescriptor;
+
+public:
+  CloseFileRunnable(const FileDescriptor& aFileDescriptor)
+#ifdef DEBUG
+  ;
+#else
+  : mFileDescriptor(aFileDescriptor)
+  { }
+#endif
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIRUNNABLE
+
+  void Dispatch();
+
+private:
+  ~CloseFileRunnable();
+
+  void CloseFile();
+};
+
+} // namespace ipc
+} // namespace mozilla
+
+#endif // mozilla_ipc_FileDescriptorUtils_h