screen-cast: Fix window recording on HiDPI

Using the same scale for the window as the
logical monitor only works correctly when having
the experimental 'scale-monitor-framebuffer'
feature enabled.
Without this experimental feature, the stream
will contain a black screen, where the actual
window only takes a small part of it.

Therefore, use a scale of 1 for the non-
experimental case.

Patch is based on commit 3fa6a92c.

GNOME/mutter!976

src/backends/meta-screen-cast-window-stream.c

@@ -225,11 +225,15 @@ meta_screen_cast_window_stream_initable_init (GInitable     *initable,
                               G_CALLBACK (on_window_unmanaged),
                               window_stream);
 
+  if (meta_is_stage_views_scaled ())
+    scale = (int) ceilf (meta_logical_monitor_get_scale (logical_monitor));
+  else
+    scale = 1;
+
   /* We cannot set the stream size to the exact size of the window, because
    * windows can be resized, whereas streams cannot.
    * So we set a size equals to the size of the logical monitor for the window.
    */
-  scale = (int) ceil (meta_logical_monitor_get_scale (logical_monitor));
   window_stream->logical_width = logical_monitor->rect.width;
   window_stream->logical_height = logical_monitor->rect.height;
   window_stream->stream_width = logical_monitor->rect.width * scale;