[mutter] tests/clutter/timeline-interpolate: Maximize error tolerance

[verdre <jonasd src gnome org>]

commit 1eaf9e5f63c124198ac2ee67ef0c3d991a351ba6
Author: Jonas Ådahl <jadahl gmail com>
Date:   Sat Jun 6 00:25:55 2020 +0200

    tests/clutter/timeline-interpolate: Maximize error tolerance
    
    Simply to make it less flaky.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1291

 src/tests/clutter/conform/timeline-interpolate.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/tests/clutter/conform/timeline-interpolate.c 
b/src/tests/clutter/conform/timeline-interpolate.c
index aa3556b59b..db17b67848 100644
--- a/src/tests/clutter/conform/timeline-interpolate.c
+++ b/src/tests/clutter/conform/timeline-interpolate.c
@@ -15,10 +15,11 @@
 /* We are at the mercy of the system scheduler so this
  * may not be a very reliable tolerance.
  *
- * It's set as very tolerable as otherwise CI, which are
- * very prone to not get CPU time scheduled, tend to often fail.
+ * It's set as very tolerable (1 ms shorter than the frame interval) as
+ * otherwise CI, which are very prone to not get CPU time scheduled, tend to
+ * often fail.
  */
-#define TEST_ERROR_TOLERANCE 150
+#define TEST_ERROR_TOLERANCE ((TEST_TIMELINE_FPS / 4) - 1)
 
 typedef struct _TestState
 {