[gimp] app: another off-by-one chunking fix

[N/A <ell src gnome org>]

commit 6d19e9e860e6b0981dfe7ef2814532c4c76aea3a
Author: Ell <ell_se yahoo com>
Date:   Sat Dec 9 10:28:37 2017 -0500

    app: another off-by-one chunking fix

 app/display/gimpdisplayshell-draw.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-draw.c b/app/display/gimpdisplayshell-draw.c
index 68270e2..c696775 100644
--- a/app/display/gimpdisplayshell-draw.c
+++ b/app/display/gimpdisplayshell-draw.c
@@ -181,8 +181,8 @@ gimp_display_shell_draw_image (GimpDisplayShell *shell,
     }
 
   /* divide the painted area to evenly-sized chunks */
-  n_rows = ceil (h / chunk_height);
-  n_cols = ceil (w / chunk_width);
+  n_rows = ceil (h / floor (chunk_height));
+  n_cols = ceil (w / floor (chunk_width));
 
   for (r = 0; r < n_rows; r++)
     {