third_party: Amend version 2 of remote shell protocol

third_party/wayland-protocols/unstable/remote-shell/remote-shell-unstable-v1.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <protocol name="remote_shell_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,
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         This is an event to notify that the window state changed in compositor.
         The state change may be triggered by a client's request, or some user
         action directly handled by the compositor. The client may choose to
         ignore this event.
       </description>
       <arg name="state_type" type="uint"/>
     </event>
 
     <!-- Version 2 additions -->
 
+    <event name="configure" since="2">
+      <description summary="suggest a surface change">
+        The configure event asks the client to change surface state.
+
+        The origin arguments specify the position, in the compositor coordinate
+        space, of the virtual display used by the client to simulate multiple
+        displays. The client must offset window positions in set_window_geometry
+        requests by this origin in order to convert between coordinate spaces.
+
+        Clients should arrange their surface for the new state, and then send an
+        ack_configure request with the serial sent in this configure event at
+        some point before committing the new surface.
+
+        If the client receives multiple configure events before it can respond
+        to one, it is free to discard all but the last event it received.
+      </description>
+      <arg name="origin_x" type="int"/>
+      <arg name="origin_y" type="int"/>
+      <arg name="serial" type="uint"/>
+    </event>
+
+    <request name="ack_configure" since="2">
+      <description summary="ack a configure event">
+        When a configure event is received, if a client commits the
+        surface in response to the configure event, then the client
+        must make an ack_configure request sometime before the commit
+        request, passing along the serial of the configure event.
+
+        For instance, the compositor might use this information during display
+        configuration to change its coordinate space for set_window_geometry
+        requests only when the client has switched to the new coordinate space.
+
+        If the client receives multiple configure events before it
+        can respond to one, it only has to ack the last configure event.
+
+        A client is not required to commit immediately after sending
+        an ack_configure request - it may even ack_configure several times
+        before its next surface commit.
+
+        A client may send multiple ack_configure requests before committing, but
+        only the last request sent before a commit indicates which configure
+        event the client really is responding to.
+      </description>
+      <arg name="serial" type="uint" summary="the serial from the configure event"/>
+    </request>
+
     <request name="set_moving" since="2">
       <description summary="interactive move started">
         Notifies the compositor when an interactive, user-driven move of the
         surface starts. The compositor may assume that subsequent
         set_window_geometry requests are position updates until it receives a
         unset_moving request.
       </description>
     </request>
 
     <request name="unset_moving" since="2">
@@ skipping 12 matching lines @@
     </description>
 
     <request name="destroy" type="destructor">
       <description summary="Destroy the notification_surface">
         Unmap and destroy the notification surface.
       </description>
     </request>
   </interface>
 
 </protocol>