exo: Implement zcr_linux_explicit_synchronization_v1

third_party/wayland-protocols/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <protocol name="linux_explicit_synchronization_unstable_v1">
 
   <copyright>
     Copyright 2016 The Chromium Authors.
 
     Permission is hereby granted, free of charge, to any person obtaining a
     copy of this software and associated documentation files (the "Software"),
     to deal in the Software without restriction, including without limitation
     the rights to use, copy, modify, merge, publish, distribute, sublicense,
@@ skipping 59 matching lines @@
     </request>
   </interface>
 
   <interface name="zcr_synchronization_v1" version="1">
     <request name="destroy" type="destructor">
       <description summary="destroy synchronization object">
         Destroy this explicit synchronization object.
       </description>
     </request>
 
+    <enum name="error">

[reveman, 2016/10/12 19:20:20]

I included this in https://codereview.chromium.org/2397843002 so it should no
longer be needed after a rebase.

+      <entry name="invalid_fence" value="0"
+             summary="the fence specified by the client could not be imported"/>
+    </enum>
+
     <request name="set_acquire_fence">
       <description summary="set the acquire fence">
         Set the acquire fence that must be signaled before the compositor
         is allowed to read the pixels in the pending wl_buffer.
 
         The acquire state is double-buffered state, and will be applied on
         the next wl_surface.commit.
+
+        If the fence could not be imported, an INVALID_FENCE error is signaled
+        to the client.
       </description>
       <arg name="fd" type="fd" summary="fence fd"/>
     </request>
   </interface>
 
 </protocol>