diff -r 000000000000 -r 6474c204b198 gfx/layers/ipc/PLayer.ipdl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/ipc/PLayer.ipdl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* 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/. */
+
+include protocol PLayerTransaction;
+
+namespace mozilla {
+namespace layers {
+
+/**
+ * PLayer represents a layer shared across thread contexts.
+ */
+
+async protocol PLayer {
+    manager PLayerTransaction;
+
+    /**
+     * OWNERSHIP MODEL
+     *
+     * Roughly speaking, the child side "actually owns" a Layer.  This
+     * is because the parent side is the "shadow"; when the child
+     * releases a Layer, the parent's shadow is no longer meaningful.
+     *
+     * To implement this model, the concrete PLayerParent keeps a
+     * strong ref to its Layer, so the Layer's lifetime is bound to
+     * the PLayerParent's.  Then, when the Layer's refcount hits 0 on
+     * the child side, we send __delete__() from the child to parent.
+     * The parent then releases its Layer, which results in the Layer
+     * being deleted "soon" (usually immediately).
+     */
+parent:
+    async __delete__();
+};
+
+} // layers
+} // mozilla