[pitivi] thumbnailsink.py: set alphamask so transparent thumbnails render

[Edward Hervey <edwardrv src gnome org>]

commit bbba32c1a8a23f21f5b8339edd2de1aca618fc1f
Author: Brandon Lewis <brandon_lewis alum berkeley edu>
Date:   Fri Jan 15 15:55:47 2010 -0800

    thumbnailsink.py: set alphamask so transparent thumbnails render

 pitivi/elements/thumbnailsink.py |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/pitivi/elements/thumbnailsink.py b/pitivi/elements/thumbnailsink.py
index af82972..2bc4ed9 100644
--- a/pitivi/elements/thumbnailsink.py
+++ b/pitivi/elements/thumbnailsink.py
@@ -50,6 +50,7 @@ class CairoSurfaceThumbnailSink(gst.BaseSink):
                                   "blue_mask = (int)  0xFF000000, "
                                   "green_mask = (int) 0x00FF0000, "
                                   "red_mask = (int)   0x0000FF00, "
+                                  "alpha_mask = (int) 0x000000FF, "
                                   "width = (int) [ 1, max ], "
                                   "height = (int) [ 1, max ], "
                                   "framerate = (fraction) [ 0, max ]"))