Make close window button lives

lib/ui/screens/call_screen.dart

@@ -36,11 +36,17 @@ class CallScreen extends StatefulWidget {
   /// String which is the title of the conversation
   final PreferredSizeWidget Function(String) buildCustomAppBar;
 
+  /// Execute custom action when the call is closed
+  ///
+  /// The default behavior is to pop the page
+  final void Function() onClose;
+
   const CallScreen({
     Key key,
     @required this.convID,
     this.floatingButtons = true,
     this.buildCustomAppBar,
+    this.onClose,
   })  : assert(convID != null),
         assert(convID > 0),
         assert(floatingButtons != null),
@@ -198,7 +204,10 @@ class _CallScreenState extends SafeState<CallScreen> {
             context: context,
             message: tr("Do you really want to leave this call ?"))) return;
 
-    MainController.of(context).popPage();
+    if (widget.onClose == null)
+      MainController.of(context).popPage();
+    else
+      widget.onClose();
   }
 
   /// Start streaming on our end

lib/ui/widgets/tablet_mode/calls/call_window_widget.dart

@@ -63,6 +63,7 @@ class _CallWindowWidgetState extends State<CallWindowWidget> {
                 )),
             convID: widget.convID,
             floatingButtons: false,
+            onClose: widget.onClose,
           ),
         ),
         feedback: Container(