Add desktop focus state change event

This change add a new event for desktop window focus state change.
With this change, ARC can have different behavior when Chrome window
or ChromeOS desktop get activated.

BUG=b:171450038
TEST=Active different window between Chrome/ARC and logcat events

Change-Id: I11cee5d5279ad12524092518cadd05fff67bab72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519686
Commit-Queue: Shengsong Tan <sstan@google.com>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827122}

components/exo/wayland/zcr_remote_shell.cc

@@ -1132,6 +1132,18 @@ class WaylandRemoteShell : public ash::TabletModeObserver,
       lost_active_surface_resource = nullptr;
     }
 
+    uint32_t focus_state;
+    if (gained_active_surface_resource) {
+      focus_state = ZCR_REMOTE_SHELL_V1_DESKTOP_FOCUS_STATE_CLIENT_FOCUSED;
+    } else if (gained_active) {
+      focus_state = ZCR_REMOTE_SHELL_V1_DESKTOP_FOCUS_STATE_OTHER_CLIENT_FOCUSED;
+    } else {
+      focus_state = ZCR_REMOTE_SHELL_V1_DESKTOP_FOCUS_STATE_NO_FOCUS;
+    }
+
+    zcr_remote_shell_v1_send_desktop_focus_state_changed(remote_shell_resource_,
+                                                         focus_state);
+
     zcr_remote_shell_v1_send_activated(remote_shell_resource_,
                                        gained_active_surface_resource,
                                        lost_active_surface_resource);

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

@@ -38,7 +38,7 @@
     reset.
   </description>
 
-  <interface name="zcr_remote_shell_v1" version="29">
+  <interface name="zcr_remote_shell_v1" version="30">
     <description summary="remote_shell">
       The global interface that allows clients to turn a wl_surface into a
       "real window" which is remotely managed but can be stacked, activated
@@ -274,6 +274,24 @@
       <arg name="use_default_device_scale_factor" type="int" summary="0 if false"/>
     </request>
 
+    <!-- Version 30 additions -->
+
+    <enum name="desktop_focus_state">
+      <description summary="desktop foucs state">
+	Desktop client window focus state.
+      </description>
+      <entry name="no_focus" value="1" summary="no window get focused"/>
+      <entry name="client_focused" value="2" summary="client window get focused"/>
+      <entry name="other_client_focused" value="3" summary="other client window get focused"/>
+    </enum>
+
+    <event name="desktop_focus_state_changed" since="30">
+      <description summary="desktop window focus state change">
+	Notifies client that the window focus state change.
+      </description>
+      <arg name="focus_state" type="uint"/>
+    </event>
+
   </interface>
 
   <interface name="zcr_remote_surface_v1" version="27">