Disable virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html on mac rel

The test is flaking on the trybots with timeout

Bug: 869800
No-presubmit: True
No-try: True
Change-Id: I3e4c3c500f2d965dc443d0cf01e7e278cb41b992
Reviewed-on: https://chromium-review.googlesource.com/1158524
Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579771}
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index d8824bc..69c9e4a 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -4866,3 +4866,4 @@
 
 # Sheriff 2018-08-01
 crbug.com/869773 [ Mac Linux ] http/tests/misc/window-dot-stop.html [ Pass Failure ]
+crbug.com/869800 [ Mac Release ] virtual/outofblink-cors/http/tests/xmlhttprequest/timeout/xmlhttprequest-timeout-worker-aborted.html [ Pass Timeout ]