[mutter] clutter/stage: Fix framebuffer capture origin offset

[Rui Matos <rtcm src gnome org>]

commit 5fbb4793017b1891f0de4720a9793e8cfc1c8483
Author: Rui Matos <tiagomatos gmail com>
Date:   Mon Sep 19 17:22:32 2016 +0200

    clutter/stage: Fix framebuffer capture origin offset
    
    Commit f36fa53b0e8b7e2389ea2b63516a2eb00fcc7aa5 had the offset math
    wrong and the reviewer didn't notice it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771502

 clutter/clutter/clutter-stage.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/clutter/clutter/clutter-stage.c b/clutter/clutter/clutter-stage.c
index b7489bc..1d2c0bc 100644
--- a/clutter/clutter/clutter-stage.c
+++ b/clutter/clutter/clutter-stage.c
@@ -4712,8 +4712,8 @@ capture_view (ClutterStage          *stage,
   clutter_stage_view_get_layout (view, &view_layout);
 
   cogl_framebuffer_read_pixels_into_bitmap (framebuffer,
-                                            view_layout.x - rect->x,
-                                            view_layout.y - rect->y,
+                                            view_layout.x + rect->x,
+                                            view_layout.y + rect->y,
                                             COGL_READ_PIXELS_COLOR_BUFFER,
                                             bitmap);