This test has been failing for all visible history.
I was able to reproduce the failing by running it in iterations. Here is the command I used: 'run-webkit-tests --root debug-256764 fast/images/slower-decoding-than-animation-image.html -1 -f --iterations 5000 --debug' and it failed 32 times.
@@ -3,7 +3,7 @@
On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
-PASS internals.imageFrameIndex(image) is 1
+FAIL internals.imageFrameIndex(image) should be 1. Was 0.
PASS successfullyParsed is true
Set expectations here: https://trac.webkit.org/changeset/256771/webkit
*** Bug 172666 has been marked as a duplicate of this bug. ***
Created attachment 394349 [details]
Committed r258930: <https://trac.webkit.org/changeset/258930>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 394349 [details].
A follow up patch which makes the test reliable on the slow bots:
Committed r258960: <https://trac.webkit.org/changeset/258960>