[orca] Start listening for window:destroy events

[Joanmarie Diggs <joanied src gnome org>]

commit 4d1d27275254323d2f6b40a22a6babb8d424c4ea
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon Feb 24 17:21:46 2020 +0100

    Start listening for window:destroy events
    
    Right now we do nothing (other than print some debugging info). But we
    may need to use these events to handle switchers which fail to emit some
    other much-needed events.

 src/orca/scripts/default.py | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/src/orca/scripts/default.py b/src/orca/scripts/default.py
index ecd08b8ce..fcdab3819 100644
--- a/src/orca/scripts/default.py
+++ b/src/orca/scripts/default.py
@@ -601,6 +601,8 @@ class Script(script.Script):
             self.onWindowDeactivated
         listeners["window:create"]                          = \
             self.onWindowCreated
+        listeners["window:destroy"]                          = \
+            self.onWindowDestroyed
 
         return listeners
 
@@ -2849,6 +2851,11 @@ class Script(script.Script):
 
         pass
 
+    def onWindowDestroyed(self, event):
+        """Callback for window:destroy accessibility events."""
+
+        pass
+
     def onWindowDeactivated(self, event):
         """Called whenever a toplevel window is deactivated.