diff -r 000000000000 -r 6474c204b198 ipc/glue/BackgroundChild.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/glue/BackgroundChild.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,72 @@
+/* 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_backgroundchild_h__
+#define mozilla_ipc_backgroundchild_h__
+
+#include "base/process.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/Transport.h"
+
+class nsIIPCBackgroundChildCreateCallback;
+
+namespace mozilla {
+namespace dom {
+
+class ContentChild;
+class ContentParent;
+
+} // namespace dom
+
+namespace ipc {
+
+class PBackgroundChild;
+
+// This class allows access to the PBackground protocol. PBackground allows
+// communication between any thread (in the parent or a child process) and a
+// single background thread in the parent process. Each PBackgroundChild
+// instance is tied to the thread on which it is created and must not be shared
+// across threads. Each PBackgroundChild is unique and valid as long as its
+// designated thread lives.
+//
+// Creation of PBackground is asynchronous. GetForCurrentThread() will return
+// null until the sequence is complete. GetOrCreateForCurrentThread() will start
+// the creation sequence and will call back via the
+// nsIIPCBackgroundChildCreateCallback interface when completed. Thereafter
+// (assuming success) GetForCurrentThread() will return the same actor every
+// time.
+//
+// The PBackgroundChild actor and all its sub-protocol actors will be
+// automatically destroyed when its designated thread completes.
+class BackgroundChild MOZ_FINAL
+{
+  friend class mozilla::dom::ContentChild;
+  friend class mozilla::dom::ContentParent;
+
+  typedef base::ProcessId ProcessId;
+  typedef mozilla::ipc::Transport Transport;
+
+public:
+  // See above.
+  static PBackgroundChild*
+  GetForCurrentThread();
+
+  // See above.
+  static bool
+  GetOrCreateForCurrentThread(nsIIPCBackgroundChildCreateCallback* aCallback);
+
+private:
+  // Only called by ContentChild or ContentParent.
+  static void
+  Startup();
+
+  // Only called by ContentChild.
+  static PBackgroundChild*
+  Alloc(Transport* aTransport, ProcessId aOtherProcess);
+};
+
+} // namespace ipc
+} // namespace mozilla
+
+#endif // mozilla_ipc_backgroundchild_h__