diff -r 000000000000 -r 6474c204b198 layout/ipc/PRenderFrame.ipdl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/ipc/PRenderFrame.ipdl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,64 @@
+/* -*- 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 PBrowser;
+include protocol PLayerTransaction;
+
+
+using class nsRegion from "nsRegion.h";
+
+namespace mozilla {
+namespace layout {
+
+/**
+ * PRenderFrame (in the layout sense of "frame") represents one web
+ * "page".  It's used to graft content processes' layer trees into
+ * chrome's rendering path.  The lifetime of a PRenderFrame is tied to
+ * its PresShell in the child process.
+ *
+ * The child process conceptually "owns" a PRenderFrame, because it
+ * only makes sense wrt documents loaded by the child.
+ */
+sync protocol PRenderFrame
+{
+    manager PBrowser;
+    manages PLayerTransaction;
+
+parent:
+    /**
+     * Shadow layer trees can be grafted into the parent's in one of
+     * two ways
+     *  - direct shadow tree: updates are sent to parent
+     *  - indirect: the parent holds a reference (ID) to a shadow tree
+     *    that's managed by the compositor.  During composition, the
+     *    shadow tree is looked up and grafted appropriately
+     *
+     * |id| is set to 0 in the "direct" case, and to a whole number
+     * in the "indirect" case.
+     */
+    async PLayerTransaction();
+
+    async NotifyCompositorTransaction();
+
+    async UpdateHitRegion(nsRegion aRegion);
+
+    async __delete__();
+
+state EMPTY_OR_DIRECT_COMPOSITOR:
+    recv PLayerTransaction goto HAVE_CONTENT;
+    recv NotifyCompositorTransaction goto EMPTY_OR_DIRECT_COMPOSITOR;
+    recv UpdateHitRegion goto EMPTY_OR_DIRECT_COMPOSITOR;
+    recv __delete__;
+
+state HAVE_CONTENT:
+    recv NotifyCompositorTransaction goto HAVE_CONTENT;
+    recv UpdateHitRegion goto HAVE_CONTENT;
+    recv __delete__;
+};
+
+} // namespace layout
+} // namespace mozilla