bug 1204171 - make mai_util_add_key_event_listener return the correct listener id r=davidb

The listener id is postincremented as a subexpression of being inserted into
the hash table.  That means the key inserted into the table is 1 less than the
value returned from the function.  Which means that later attempts to remove
the returned id will fail because that hash table knows about a different id.

accessible/atk/UtilInterface.cpp

@@ -265,7 +265,8 @@ mai_util_add_key_event_listener(AtkKeySnoopFunc listener, gpointer data)
   }
   AtkKeySnoopFuncPointer atkKeySnoop;
   atkKeySnoop.func_ptr = listener;
-  g_hash_table_insert(sKey_listener_list, GUINT_TO_POINTER(key++),
+  key++;
+  g_hash_table_insert(sKey_listener_list, GUINT_TO_POINTER(key),
                       atkKeySnoop.data);
   return key;
 }