wayland-protocols: Add pointer_stylus_exists error to zcr_stylus_v1 interface.

third_party/wayland-protocols/unstable/stylus/stylus-unstable-v1.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <protocol name="stylus_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,
     and/or sell copies of the Software, and to permit persons to whom the
     Software is furnished to do so, subject to the following conditions:
 
     The above copyright notice and this permission notice (including the next
     paragraph) shall be included in all copies or substantial portions of the
     Software.
 
     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
     THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     DEALINGS IN THE SOFTWARE.
   </copyright>
 
-  <interface name="zcr_stylus_v1" version="1">
+  <interface name="zcr_stylus_v1" version="2">
     <description summary="extends wl_pointer with events for on-screen stylus">
       Allows a wl_pointer to represent an on-screen stylus. The client can
       interpret the on-screen stylus like any other mouse device, and use
       this protocol to obtain detail information about the type of stylus,
       as well as the force and tilt of the tool.
 
       These events are to be fired by the server within the same frame as other
       wl_pointer events.
 
       Warning! The protocol described in this file is experimental and
       backward incompatible changes may be made. Backward compatible changes
       may be added together with the corresponding uinterface version bump.
       Backward incompatible changes are done by bumping the version number in
       the protocol and uinterface names and resetting the interface version.
       Once the protocol is to be declared stable, the 'z' prefix and the
       version number in the protocol and interface names are removed and the
       interface version number is reset.
     </description>
 
+    <enum name="error">
+      <entry name="pointer_stylus_exists" value="0"
+             summary="the pointer already has a pointer_stylus object associated"/>
+    </enum>
+
     <request name="get_pointer_stylus">
       <description summary="get stylus interface for pointer">
         Create pointer_stylus object. See zcr_pointer_stylus_v1 interface for
-        details.
+        details. If the given wl_pointer already has a pointer_stylus object
+        associated, the pointer_stylus_exists protocol error is raised.
       </description>
       <arg name="id" type="new_id" interface="zcr_pointer_stylus_v1"/>
       <arg name="pointer" type="object" interface="wl_pointer"/>
     </request>
   </interface>
 
   <interface name="zcr_pointer_stylus_v1" version="1">
     <description summary="stylus extension for pointer">
       The zcr_pointer_stylus_v1 interface extends the wl_pointer interface with
       events to describe details about a stylus acting as a pointer.
@@ skipping 48 matching lines @@
         [-90,90]. A positive x is to the right and a positive y is towards the
         user.
       </description>
       <arg name="time" type="uint" summary="timestamp with millisecond granularity"/>
       <arg name="tilt_x" type="fixed" summary="tilt in x direction"/>
       <arg name="tilt_y" type="fixed" summary="tilt in y direction"/>
     </event>
   </interface>
 
 </protocol>