diff -r 000000000000 -r 6474c204b198 ipc/glue/BackgroundParent.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/glue/BackgroundParent.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,83 @@
+/* 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_backgroundparent_h__
+#define mozilla_ipc_backgroundparent_h__
+
+#include "base/process.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ipc/Transport.h"
+
+template <class> class already_AddRefed;
+
+namespace mozilla {
+namespace dom {
+
+class ContentParent;
+
+} // namespace dom
+
+namespace ipc {
+
+class PBackgroundParent;
+
+// This class is not designed for public consumption beyond the few static
+// member functions.
+class BackgroundParent MOZ_FINAL
+{
+  friend class mozilla::dom::ContentParent;
+
+  typedef base::ProcessId ProcessId;
+  typedef mozilla::dom::ContentParent ContentParent;
+  typedef mozilla::ipc::Transport Transport;
+
+public:
+  // This function allows the caller to determine if the given parent actor
+  // corresponds to a child actor from another process or a child actor from a
+  // different thread in the same process.
+  // This function may only be called on the background thread.
+  static bool
+  IsOtherProcessActor(PBackgroundParent* aBackgroundActor);
+
+  // This function returns the ContentParent associated with the parent actor if
+  // the parent actor corresponds to a child actor from another process. If the
+  // parent actor corresponds to a child actor from a different thread in the
+  // same process then this function returns null.
+  // This function may only be called on the background thread. However,
+  // ContentParent is not threadsafe and the returned pointer may not be used on
+  // any thread other than the main thread. Callers must take care to use (and
+  // release) the returned pointer appropriately.
+  static already_AddRefed<ContentParent>
+  GetContentParent(PBackgroundParent* aBackgroundActor);
+
+private:
+  // Only called by ContentParent for cross-process actors.
+  static PBackgroundParent*
+  Alloc(ContentParent* aContent,
+        Transport* aTransport,
+        ProcessId aOtherProcess);
+};
+
+// Implemented in BackgroundImpl.cpp.
+bool
+IsOnBackgroundThread();
+
+#ifdef DEBUG
+
+// Implemented in BackgroundImpl.cpp.
+void
+AssertIsOnBackgroundThread();
+
+#else
+
+inline void
+AssertIsOnBackgroundThread()
+{ }
+
+#endif // DEBUG
+
+} // namespace ipc
+} // namespace mozilla
+
+#endif // mozilla_ipc_backgroundparent_h__